Ventilation system for manhole vault

ABSTRACT

A system for use with a manhole vault having an internal atmosphere, and, optionally, with a ventilation stack connecting the vault to an external atmosphere. The system includes a manhole cover, a ventilation pipe, and an air moving assembly. The cover has one or more through-holes extending between top and bottom surfaces. Each of the through-hole(s) is in fluid communication with the external atmosphere at the top surface. The pipe has a through-channel that extends between first and second openings. The first opening is positioned proximal to either an opening into the ventilation stack or at least one of the through-hole(s) at the bottom surface of the cover. The second opening is positioned in the interior of the vault. The device is configured to cause a portion of one of the interior and external atmospheres to flow through the through-channel toward a different one of the interior and external atmospheres.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of U.S. Provisional Application No.62/171,803, filed on Jun. 5, 2015, which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention is directed generally to methods and devices forventilating underground chambers, such as manhole vaults.

Description of the Related Art

Underground utilities, such as water, sewer, natural gas, electricity,telephone, cable, and steam, are a common means of delivering theessentials of modern life in a developed society. Referring to FIG. 1 ,such utilities are often routed through an underground system 10 thatincludes a plurality of substantially identical underground chambers ormanhole vaults 12 and 14 interconnected by one or more conduits 20A-20C.The vaults 12 and 14 may each be configured to house critical controlequipment, monitoring equipment, and appropriate network connections.

As shown in FIG. 1 , the vaults 12 and 14 and the conduit(s) 20A-20C arepositioned below a street or sidewalk level (identified as a surface30). In FIG. 1 , only the two vaults 12 and 14 of the system 10 havebeen illustrated. However, the system 10 may include any number ofvaults each substantially similar to one of the vaults 12 and 14.Similarly, only the three conduits 20A-20C have been illustrated.However, the system 10 may include any number of conduits eachsubstantially similar to one of the conduits 20A-20C.

Because the vaults 12 and 14 are substantially identical to one another,for the sake of brevity, only the vault 12 will be described in detail.In FIG. 1 , equipment (e.g., electrical equipment), commonly foundwithin the vault 12 has been omitted for the sake of clarity. The vault12 has an interior 50 with a rectangular prism-shaped main chamber 52.The main chamber 52 is defined by one or more sidewalls 54 that extendbetween a ceiling 56 and a floor 58. The conduits 20A-20C may pass atleast partially through the main chamber 52. A cylindrical passageway 60(also referred to as a “neck”) defined by one or more wall(2) 64provides personnel access (e.g., for a worker 61) to the main chamber 52from the surface 30. The neck 60 is usually about 3 feet in diameter andgenerally extends at least about 3 feet below the surface 30. The neck60 leads to a manhole 62, which is traditionally capped with aconventional manhole cover, such as a vented manhole cover 70 (see FIG.2 ). The vented manhole cover 70 illustrated in FIG. 2 is a design oftenemployed by Consolidated Edison (“ConEd”) of New York. The manhole cover(e.g., the vented manhole cover 70 illustrated in FIG. 2 ) is fittedwithin a recess 63 in the manhole 62 and provides a measure of securitywith respect to pedestrian and vehicular traffic.

Underground electrical utilities are typically preferred over aboveground systems because underground systems make efficient use of limitedsurface and air space in urban environments and preserve aesthetics insuburban environments. Underground systems are generally more securethan overhead circuits and, when well maintained, provide reliableservice to the public.

Unfortunately, underground electrical utilities also present fire and/orexplosion hazards proximate to areas of human habitation. For example,while the conduits 20A-20C provide passageways between the vaults 12 and14 for interconnecting electrical cables, the conduits 20A-20C alsoallow air, gases, vapors, and water to enter the interiors 50 of thevaults 12 and 14. It is not unusual for such underground vaults andconduits to fill with water depending on the surface topography, watertable, and recent precipitation. Water also enters through the cover.Water allows for electro-chemical breakdown of the insulation to occurthrough tracking of cables in ducts (i.e., electrical discharge alongdegraded insulation) and electrical equipment failures inside one ormore of the vaults 12 and 14, which produce hazardous concentrations ofexplosive and flammable gases within one or more of the vaults 12 and14. Because air can never be excluded entirely from the vault 12,manhole events may result. Manhole events include both minor incidents(such as smoke or small fires) and/or major events (such as sustainedfires and explosions). At best, a minor incident is likely to cause anelectrical power outage. At worst, a major event, such as an explosion,can occasionally propel a manhole cover skyward causing property damage,injuries, and even death.

According to a paper by Rudin et al. (“A process for predicting manholeevents in Manhattan,” Mach Learn (2010) 80: 1-31), there were 6670“serious event tickets” written for a total of 250,000 manholes in theConEd (N.Y.) system over a ten-year period ending in 2006. In otherwords, the chance that a manhole will have a serious event in a givenyear is about 1 in 375. Incident rates in this range suggest, at aminimum, a need for regular inspection and maintenance of manholevaults. Surprisingly, a report prepared for a Washington, D.C. utilityindicated that such routine visits did not reduce the incidence rate ofserious events (Siemens, Inc., Report #R55-11, “Investigation of ManholeIncidents Occurring Around and in the Underground Distribution System ofthe Potomac Electric Power Company,” Jun. 30, 2011). Thus, other, moreproactive measures are often employed, but as indicated in the followingexamples, each has been shown to have at least one major shortcoming.

For example, the manhole cover may be tethered (e.g., to the surface 30)to prevent the manhole cover from being launched beyond the length ofthe tether in the event of an explosion. Unfortunately, this approachdoes not prevent smoke and/or flames from spilling out of the manhole,which presents an unacceptable public hazard, or at least a nuisance.

Another approach is to substitute a light-weight manhole cover in placeof the typically heavy metal manhole cover. This approach can reducedamage to structures, vehicles, and people because the light-weightmanhole cover will lift more quickly in the event of an explosion. But,as with the aforementioned tethering approach, the issues of smoke andflames remain. Additional drawbacks to this approach include initialcost and questionable service life.

Some have suggested using electronic sensors to monitor the vaultenvironment and transmit warning notices but this mitigation method isrelatively expensive. Further, the electronics employed are somewhatunreliable given the usually harsh environment inside the vault andrequired long life-spans.

Yet another approach is to seal the conduits 20A-20C (that may houseelectrical cables) running between vaults 12 and 14 to minimize airentry therein, which produces a fuel-rich, oxygen-starved, environmentinside the conduits 20A-20C. Unfortunately, this fuel-rich environmentincludes flammable gases that ultimately find ways out of the conduits20A-20C (whether plugged or not) and into one or more of the vault(s) 12and 14 connected to the conduits 20A-20C. This collection of flammablegases inside one or more of the vaults 12 and 14 can result in a manholeexplosion that is more dangerous than a manhole that is merely smoking(referred to as a “smoker”).

Some (see U.S. Pat. No. 6,012,532) have proposed limiting airflow withinthe vault by positioning an inflatable bladder inside the vault andfilling the bladder with an inert gas that expands the bladder into theopen volume in the vault. Unfortunately, this approach is impracticalbecause the bladder must be deflated and re-inflated each time themanhole vault requires access, which is a large amount of work.

Referring to FIG. 2 , using yet another approach, ConEd has installedvented manhole covers (like the vented manhole cover 70) that allowdangerous vault gases to escape from the vault. Unfortunately, ventopenings or holes (e.g., vent holes 72) in the vented manhole coverpresent drawbacks of their own. The vented manhole cover 70 providesabout 25% open space but contains no water mitigating features. Thus,the vent holes 72 allow more precipitation and corrosive road chemicals(e.g., road salt and other deicers) to enter the vault and such ingresshas been implicated in circuit failures and manhole events. They alsoincrease the likelihood that hazardous liquids, trash, human waste,and/or vermin will enter the vault—all of which can produce flammablevapors, either directly (e.g., a fuel spill) or indirectly bybiodegradation of organic materials. Finally, the vent holes 72 caninvite disposal of bio-hazards, such as used hypodermic syringes, intothe vault, which slow any required maintenance because specialprocedures are necessary before personnel can enter the vault.

It is therefore apparent that a need exists for methods, equipment,and/or apparatus that effectively reduce the frequency and/or severityof manhole events. The present application provides these and otheradvantages as will be apparent from the following detailed descriptionand accompanying figures.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a cross-sectional view of a prior art underground systemincluding a plurality of manhole vaults interconnected by a plurality ofconduits.

FIG. 2 is a top view of a prior art vented manhole cover.

FIG. 3 is a block diagram of a ventilation system for use in at leastone of the manhole vaults of the underground system of FIG. 1 .

FIG. 4A is a cross-sectional view of an exemplary implementation of afirst embodiment of the ventilation system including a manhole cover andan air moving assembly installed within one of the manhole vaults of theunderground system of FIG. 1 .

FIG. 4B is a cross-sectional view of an alternate exemplaryimplementation of the first embodiment of the ventilation system.

FIG. 5A is an enlarged view of a portion of FIG. 4A identified by abroken line box 5A in FIG. 4A.

FIG. 5B is a cross-sectional view of a manhole cover coupled to aventilation pipe by a coupling flange.

FIG. 5C is an enlarged cross-sectional view of a waterproof sealpositioned between the manhole cover and a ring support of FIG. 5A.

FIG. 6A is a top view of an alternate exemplary implementation of thefirst embodiment of the ventilation system that includes a manhole coverand a ring support.

FIG. 6B is an enlarged view of a portion of FIG. 6A identified by acircle 6B in FIG. 6A.

FIG. 6C is a cross-sectional view taken through a line 6C-6C in FIG. 6A.

FIG. 7 is a cross-sectional view of an alternate exemplaryimplementation of the first embodiment of the ventilation system thatincludes a manifold that couples the ventilation pipe to the manholecover.

FIG. 8A is an isometric view of an alternate exemplary implementation ofthe first embodiment of the ventilation system that includes a manholecover and vent and exhaust hole plugs.

FIG. 8B is an exploded view of the implementation of the firstembodiment of the ventilation system depicted in FIG. 8A.

FIG. 8C is a top view of the implementation of the first embodiment ofthe ventilation system depicted in FIG. 8A.

FIG. 8D is a bottom view of the implementation of the first embodimentof the ventilation system depicted in FIG. 8A.

FIG. 8E is an isometric view of the manhole cover shown in FIG. 8Aomitting the vent and exhaust hole plugs.

FIG. 8F is a cross-sectional view taken through a line 8F-8F in FIG. 8A.

FIG. 8G is an enlarged view of a portion of FIG. 8F identified by abroken line box 8G in FIG. 8F.

FIG. 8H is a cross-sectional view taken through a line 8H-8H in FIG. 8A.

FIG. 8I is an enlarged view of a portion of FIG. 8H identified by abroken line box 8I in FIG. 8H.

FIG. 9A is a cross-sectional view of an alternate exemplaryimplementation of the first embodiment of the ventilation system.

FIG. 9B is an enlarged view of a portion of FIG. 9A identified by abroken line box 9B in FIG. 9A.

FIG. 10A is an exploded view of an alternate exemplary implementation ofthe first embodiment of the ventilation system that includes a manholecover, an exhaust passage cap, and round vent hole plugs.

FIG. 10B is a top view of the implementation of the first embodiment ofthe ventilation system depicted in FIG. 10A.

FIG. 10C is a top view of the manhole cover shown in FIG. 10A omittingthe exhaust passage cap and the round vent hole plugs.

FIG. 10D is a cross-sectional view taken through a line 10D-10D in FIG.10B.

FIG. 10E is a cross-sectional view taken through a line 10E-10E in FIG.10B.

FIG. 10F is an enlarged view of a portion of FIG. 10D identified by abroken line box 10F in FIG. 10D.

FIG. 10G is an isometric view of the exhaust passage cap shown in FIG.10A.

FIG. 11A is a top view of an alternate exemplary implementation of amanifold for use in the ventilation system.

FIG. 11B is a side view of the manifold of FIG. 11A.

FIG. 11C is an isometric view of the manifold of FIG. 11A.

FIG. 12 is side view of a float assembly including a bellows attached toa float subassembly.

FIG. 13A is a left side view of an in-line heater with a cutaway portionshowing an electric cartridge heater.

FIG. 13B is a front view of the in-line heater of FIG. 13A.

FIG. 13C is a bottom view of the in-line heater of FIG. 13A.

FIG. 14A is a front view of an in-line fan.

FIG. 14B is a right side view of the in-line fan of FIG. 14A with acutaway portion showing fan blades.

FIG. 14C is a bottom view of the in-line fan of FIG. 14A.

FIG. 15 is a detailed isometric view of the exhaust hole plug for usewith the implementation of the first embodiment of the ventilationsystem depicted in FIG. 8A.

FIG. 16 is a detailed isometric view of the vent hole plug for use withthe implementation of the first embodiment of the ventilation systemdepicted in FIG. 8A.

FIG. 17A is a top view of the vent hole plug for use with theimplementation of the first embodiment of the ventilation systemdepicted in FIG. 10A.

FIG. 17B is a side view of the round vent hole plug of FIG. 17A.

FIG. 17C is an isometric view of the round vent hole plug of FIG. 17A.

FIG. 18 is a cross-sectional view of an exemplary implementation of asecond embodiment of the ventilation system for use with a manhole vaultconnected to an external atmosphere by a vent stack.

FIG. 19 is a cross-sectional view of an exemplary implementation of athird embodiment of the ventilation system.

FIG. 20 is a side perspective view of an exemplary implementation of anopen second end of the ventilation pipe of the ventilation system.

FIG. 21A is a perspective view of an exemplary implementation of afourth embodiment of the ventilation system including a manhole cover, asupport bracket assembly, and a ventilator assembly.

FIG. 21B is a perspective view of an underside of the implementationdepicted in FIG. 21A.

FIG. 22A is a perspective view of a top side of the manhole cover of theimplementation depicted in FIG. 21A.

FIG. 22B is a perspective view of a bottom side of the manhole cover ofthe implementation depicted in FIG. 21A.

FIG. 23 is a perspective view of the support bracket assembly includinga support frame and a plurality of mounting assemblies.

FIG. 24 is a perspective view of an underside of the support frame ofthe support bracket assembly.

FIG. 25 is an exploded perspective view of one of the mountingassemblies of the support bracket assembly.

FIG. 26A is a perspective view into the manhole vault with the manholecover of the implementation depicted in FIG. 21A removed.

FIG. 26B is a top view of the fourth embodiment of the ventilationsystem with the manhole cover removed.

FIG. 27 is a perspective view of the ventilator assembly of theimplementation depicted in FIG. 21A.

FIG. 28 is a perspective view of a fan assembly of the ventilatorassembly of FIG. 27 .

FIG. 29 is a perspective view of the fan assembly of FIG. 28 with one ofits panels removed to reveal structures inside the fan assembly.

FIG. 30 is a cross-sectional view of the ventilator assembly takenthrough a line 30-30 in FIG. 27 .

FIG. 31 is a side view of the implementation of the ventilation systemdepicted in FIG. 21A.

FIG. 32 is a side view of the implementation of the ventilation systemdepicted in FIG. 21A installed in one of a plurality of manhole vaultsinterconnected by a plurality of conduits.

FIG. 33 is a perspective view of the fan assembly of FIG. 28 with one ofits panels removed including an optional debris catcher.

FIG. 34 is a section view of a test apparatus used to evaluate variousmanhole cover designs.

FIG. 35 is a plot of the time needed to clear a heavier-than-air vaporfrom the vault of the apparatus shown in FIG. 34 as a function of windspeed over various manhole cover designs.

FIG. 36 is a plot comparing clearing times for argon and artificial fogin the apparatus shown in FIG. 34 as a function of wind speed overmanhole cover Assembly 2.

DETAILED DESCRIPTION OF THE INVENTION Overview

FIG. 3 is block diagram of a ventilation system 100 for use in one ormore of the vaults 12 and 14 (see FIG. 1 ) of the underground system 10(see FIG. 1 ). In FIG. 3 , the ventilation system 100 has beenillustrated as being installed in the vault 12. For ease ofillustration, the conduits 20B and 20C (see FIG. 1 ) have been omittedfrom FIG. 3 . In the embodiment illustrated, each of the conduits20A-20C (see FIG. 1 ) houses a cable 110 that has a conductor 112surrounded by an outer layer 114 constructed from one or more cableinsulation materials and/or cable shield materials. The vault 12 mayhouse equipment 84 (e.g., electrical equipment). The vault 12 may alsohouse undesirable materials, such as water 80 (e.g., flood water) and/ordebris 82 (e.g., hazardous liquids, road salt, trash, human waste,vermin, hypodermic syringes, etc.).

The ventilation system 100 includes an air moving assembly 90 and aninterface 92 between an external atmosphere 102 (e.g., above the surface30) outside the vault 12 and an internal atmosphere 104 inside the vault12. The internal atmosphere 104 may include an undesired (andpotentially dangerous) gaseous composition 106. The gaseous composition106 may be non-uniformly distributed within the interior 50 of the vault12. For example, the gaseous composition 106 may be adjacent or near thefloor 58. Gases (that contribute to the gaseous composition 106) mayresult from electrochemical degradation of the outer layer 114 or aportion thereof (e.g., cable insulation). Further, electrical trackingmay heat and decompose the outer layer 114 or a portion thereof (e.g.,cable insulation) to create gases (that contribute to the gaseouscomposition 106).

All or a portion of the air moving assembly 90 may be positioned insidethe internal atmosphere 104 of the vault 12. Optionally, the air movingassembly 90 may include an air-moving device 94 (e.g., a ventilator).However, this is not a requirement. The air-moving device 94 may becontrolled at least in part by a timer 87 that may be positioned insideor outside the vault 12. The timer 87 may be operable to turn theair-moving device 94 on or off at predetermined times. In this manner,the timer 87 may cycle the air-moving device 94 on/off at predeterminedtimes (e.g., regular intervals, scheduled times, and the like). Forexample, the timer 87 may run the air-moving device 94 less than about 5minutes every hour or less than about 15 minutes every hour.

By way of yet another non-limiting example, the air-moving device 94 maybe controlled at least in part by a limit switch 89 that shuts power offto the air-moving device 94 when the manhole cover 130 is removed and/orthe air-moving device 94 is removed.

The interface 92 may be implemented as a manhole cover 130 and/or aventilation duct or vent stack 132. The vent stack 132 may be anexisting external ventilation duct or vent stack (e.g., of the typecurrently in use in California).

In embodiments in which the interface 92 is the manhole cover 130, themanhole cover 130 includes one or more through-holes 151. A firstportion of the through-holes 151 may each function as a vent hole 152and/or a second portion of the through-holes 151 may each function as anexhaust hole 153. In other words, the manhole cover 130 may include oneor more vent holes 152 and/or one or more exhaust holes 153. Each venthole 152 is configured to allow a portion of the external atmosphere 102(represented by an arrow A1) to pass through the manhole cover 130 andenter the internal atmosphere 104. On the other hand, each exhaust hole153 is configured to allow a portion of the internal atmosphere 104(represented by an arrow A2) to pass through the manhole cover 130 andenter the external atmosphere 102. As is apparent to those of ordinaryskill in the art, because the direction of the flow through a particularone of the through-holes 151 determines whether that particularthrough-hole is a vent hole or an exhaust hole, any one of thethrough-holes 151 may be used as either a vent hole or an exhaust hole.Further, by reversing the direction of the flow, a vent hole may beconverted into an exhaust hole and vice versa. Further, one or more ofthe through-holes 151 may be configured for bi-directional flow andtherefore function as both a vent hole and an exhaust hole.

The vent hole(s) 152 and the exhaust hole(s) 153 may be sized so as tominimize the flow resistance between the external and internalatmospheres 102 and 104. For example, the ratio of the total open areaavailable for gas ingress (i.e., intake represented by the arrow A1)through the vent hole(s) 152 to that available for gas egress (i.e.,exhaust represented by the arrow A2) through the exhaust hole 153 may beabout 1.0±0.25. However, this is not a requirement. By way of anothernon-limiting example, the ratio of total open area available for gasingress (i.e., intake represented by the arrow A1) through the venthole(s) 152 to that available for gas egress (i.e., exhaust representedby the arrow A2) through the exhaust hole 153 may be adjusted (orrestricted) such that air is preferentially drawn from adjacent manholevaults (e.g., one of vaults 14 and 16), instead of entirely from thevault 12, and exhausted through the exhaust hole(s) 153. In this manner,the air moving assembly 90 in the vault 12 may be used to also draw airfrom other vaults connected thereto.

The vent hole(s) 152 may occupy at least a predetermined amount of atotal area of a top side 131 of the manhole cover 130. By way ofnon-limiting examples, the predetermined amount of the total area of thetop side 131 occupied by the vent hole(s) 152 may be about 5% or about15%.

Similarly, the exhaust hole(s) 153 may occupy at least a predeterminedamount of the total area of the top side 131 of the manhole cover 130.By way of non-limiting examples, the predetermined amount of the totalarea of the top side 131 occupied by the exhaust hole(s) 153 may beabout 5% or about 15%.

In embodiments in which the interface 92 is the ventilation stack 132,the ventilation stack 132 provides a passageway 134 in fluidcommunication with both the external and internal atmospheres 102 and104. Thus, a portion of the external atmosphere 102 (represented by anarrow A1′) may pass through the passageway 134 and enter the internalatmosphere 104. On the other hand, a portion of the internal atmosphere104 (represented by an arrow A2′) may pass through the passageway 134and enter the external atmosphere 102.

The arrows A1 and A1′ represent exterior (fresh) air flowing from theexternal atmosphere 102 into the internal atmosphere 104. On the otherhand, the arrows A2 and A2′ represent interior (stale and/orcontaminated) air flowing from the internal atmosphere 104 into theexternal atmosphere 102. Together, the arrows A1 and A2 represent an airexchange between the external and internal atmospheres 102 and 104through the manhole cover 130, and the arrows A1′ and A2′ represent anair exchange between the external and internal atmospheres 102 and 104through the ventilation stack 132.

The air moving assembly 90 causes the air exchange represented by one ormore of the arrows A1, A1′, A2, and A2′. In other words, in embodimentsin which the interface 92 includes the manhole cover 130, the air movingassembly 90 may cause at least a portion of the internal atmosphere 104(represented by the arrow A2) to be expelled outwardly from the vault 12through the exhaust hole(s) 153 in the manhole cover 130, and/or atleast a portion of the external atmosphere 102 (represented by the arrowA1) to be drawn into the vault 12 through the vent hole(s) 152 in themanhole cover 130. In embodiments in which the interface 92 includes theventilation stack 132, the air moving assembly 90 may cause at least aportion of the internal atmosphere 104 (represented by the arrow A2′) tobe expelled outwardly from the vault 12 through the passageway 134and/or at least a portion of the external atmosphere 102 (represented bythe arrow A1′) to be drawn into the vault 12 through the passageway 134.Optionally, the air-moving device 94 may be external to the vault. Forexample, the air-moving device 94 may be located within the vent stack132.

In embodiments in which the interface 92 includes the manhole cover 130,double-headed arrows A3 and A4 represent airflow inside the vault 12generated by the air moving assembly 90. In such embodiments, the airmoving assembly 90 may be configured to push (e.g., blow) internal airtoward the exhaust hole(s) 153 of the manhole cover 130, pull (e.g.,suck) external air in through the vent hole(s) 152 of the manhole cover130, or both. In embodiments in which the interface 92 includes theventilation stack 132, double-headed arrows A4 and A5 represent airflowinside the vault 12 generated by the air moving assembly 90. In suchembodiments, the air moving assembly 90 may be configured to push (e.g.,blow) internal air into the passageway 134 of the ventilation stack 132,pull (e.g., blow) external air in through the passageway 134 of theventilation stack 132, or both.

The conduits 20A-20C (see FIG. 1 ) interconnecting the vaults 12 and 14(see FIG. 1 ) provide passageways through which air (and other gases)may travel between the vaults 12 and 14 of the system 10 (see FIG. 1 ).The air moving assembly 90 may cause air (and other gases) to flow intothe internal atmosphere 104 from one or more of the conduits 20A-20C(see FIG. 1 ) and/or one or more of the neighboring vaults (via theconduits 20A-20C). Additionally, the air moving assembly 90 may causeair (and other gases) to flow out of the internal atmosphere 104 intoone or more of the conduits 20A-20C (see FIG. 1 ) and potentially intoone or more neighboring vaults (via the conduits 20A-20C). In otherwords, the air moving assembly 90 may move air between a particularvault (e.g., the vault 12) and one or more of the conduits 20A-20C (seeFIG. 1 ). Further, the air moving assembly 90 may move air between aparticular vault (e.g., the vault 12) and one or more neighboring vaultsvia the conduits 20A-20C (see FIG. 1 ).

In embodiments in which the interface 92 includes the manhole cover 130,the manhole cover 130 may be removably coupled to the air movingassembly 90. For example, the manhole cover 130 may include an accesshole (e.g., an access hole 236 depicted in FIGS. 7, 8B, 8E, 8F, and 8H)through which the worker 61 may uncouple the manhole cover 130 from theair moving assembly 90. The access hole may be covered by a removableaccess cover (e.g., an access cover 238 depicted in FIGS. 7, 8A-8C, 8F,and 8H). Optionally, the air moving assembly 90 may include a manifold(e.g., a manifold 246A depicted in FIGS. 7, 9B, and 19 , a manifold 246Ddepicted in FIGS. 8A, 8B, 8D, 8F, and 8H, or a manifold 460 depicted inFIGS. 11A-11C) positioned between the manhole cover 130 and the airmoving assembly 90. The manifold is configured to channel the internalair pushed by the air moving assembly 90 toward the exhaust hole(s) 153of the manhole cover 130 or, alternatively, to channel the external airdrawn in through the vent hole(s) 152 by the air moving assembly 90 intothe vault 12. Optionally, a coupling flange (e.g., a coupling flange 332depicted in FIGS. 5B, 7, 8B, 8F, 8H, and 9B) may be used to couple themanhole cover 130 to the air moving assembly 90. The coupling flange maybe a separate component or formed in the manhole cover 130 or themanifold.

In embodiments in which the interface 92 includes the manhole cover 130,the manhole cover 130 may be supported by a manhole ring support (e.g.,a manhole ring support 250A depicted in FIGS. 5A, 5B, 9B, and 19 , amanhole ring support 250B depicted in FIGS. 6A-6C, or a manhole ringsupport 250G depicted in FIGS. 21A, 21B, and 26 ), which is positionedinside the manhole 62 within the recess 63 (see FIG. 1 ). The manholering support may function as an adapter allowing the manhole cover 130to cap manholes having different internal sizes (e.g., internaldiameters) and/or different internal shapes.

As described in detail below, the manhole ring support, the manholecover 130, and/or the surface 30 may include features (e.g., dams,channels, and/or moats) configured to help prevent surface water (e.g.,road run-off or precipitation) from flowing into the vault 12 throughthe through-hole(s) 151. For example, the vent hole(s) 152 may bepartially covered or plugged by optional vent plugs (e.g., a vent holeplug 652D depicted in FIGS. 8A-8D, 8H, 8I, and 16 , or a vent hole plug652F depicted in FIGS. 10A, 10B, 10D-10F, and 17A-17C). Similarly, theexhaust hole(s) 153 may be covered or plugged by optional exhaust plugs(e.g., an exhaust hole plug 653D depicted in FIGS. 8A-8C, 8F, 8G, 9A, 15, and 19). The vent hole plugs 652D or 652F may each be configured tohelp prevent surface water from entering the vault 12 via one of thevent hole(s) 152. Similarly, the exhaust hole plug 653D may beconfigured to help prevent water from entering the vault 12 via one ofthe exhaust hole(s) 153.

The following embodiments provide exemplary implementations of theventilation system 100.

First Embodiment of Ventilation System

FIG. 4A depicts a first embodiment of a ventilation system 210 installedin the vault 12. In this embodiment, the interface 92 (see FIG. 3 )includes a manhole cover 230A and the air moving assembly 90 (see FIG. 3) is implemented as an air moving assembly 240. FIG. 4B depicts analternate implementation of the air moving assembly 240. The ventilationsystem 210 may include the ventilation stack 132 (see FIG. 3 ). However,this is not a requirement and the ventilation stack 132 (see FIG. 3 )has been omitted from FIGS. 4A and 4B.

FIG. 5A is an enlarged portion of FIG. 4A identified by a broken linebox 5A in FIG. 4A. Referring to FIG. 5A, optionally, the ventilationsystem 210 may include the removable access cover 238 (see FIGS. 7,8A-8C, 8F, and 8H), the manhole ring support 250A, the vent hole plug652D (see FIGS. 8A-8D, 8H, 8I, and 16 ), the vent hole plug 652F (seeFIGS. 10A, 10B, 10D-10F, and 17A-17C), and/or the exhaust hole plug 653D(see FIGS. 8A-8C, 8F, 8G, 9A, 15, and 19 ). Because external aboveground components must bear the weight of vehicular traffic, they aretypically fabricated from metal. Thus, the manhole cover 230A, theaccess cover 238 (see FIGS. 7, 8A-8C, 8F, and 8H), the manhole ringsupport 250A, the vent hole plug 652D (see FIGS. 8A-8D, 8H, 8I, and 16), the vent hole plug 652F (see FIGS. 10A, 10B, 10D-10F, and 17A-17C),and/or the exhaust hole plug 653D (see FIGS. 8A-8C, 8F, 8G, 9A, 15, and19 ) may each be constructed from metal. By way of non-limitingexamples, each of these components may be fabricated from ductile ironor cast iron when used in a location requiring a traffic rating.

As mentioned above, the ventilation system 210 includes the manholecover 240A and the air moving assembly 240.

Manhole Cover

Referring to FIG. 5A, the manhole cover 230A is configured to cap themanhole 62 instead of and in place of a conventional manhole cover(e.g., the vented manhole cover 70 illustrated in FIG. 2 or a non-ventedmanhole cover, not shown). As will be described below, the ventilationsystem 210 may include an alternate embodiment of the manhole cover 230A(e.g., one of manhole covers 230B-230G shown in FIGS. 6A, 7, 8A, 9B,10A, and 22A, respectively) instead of and in place of the manhole cover230A. Although the manhole covers 230A-230G have each been illustratedas having a traditional round manhole cover shape, each may have analternate shape, such as rectangular. Furthermore, the manhole cover230A may be implemented by retrofitting a conventional manhole cover(e.g., the vented manhole cover 70 illustrated in FIG. 2 ) by creatingthe vent hole(s) 152 (see FIG. 3 ) and/or the exhaust hole(s) 153 (seeFIG. 3 ) in an otherwise solid cover, plugging some existing holes(e.g., the vent holes 72 illustrated in FIG. 2 ), adding a manifold(e.g., like the manifold 246A) to redirect flow, adding the vent holeplug 652D (see FIGS. 8A-8D, 8H, 8I, and 16), adding the vent hole plug652F (see FIGS. 10A, 10B, 10D-10F, and 17A-17C), and/or adding theexhaust hole plug 653D (see FIGS. 8A-8C, 8F, 8G, 9A, 15, and 19 ), whereappropriate.

Referring to FIG. 5A, in the embodiment of the ventilation system 210illustrated, the manhole cover 230A is supported by the manhole ringsupport 250A (described in detail below), which is positioned inside themanhole 62. The manhole cover 230A rests on a ring-shaped bearingsurface or ledge 254A formed in the manhole ring support 250A. Referringto FIG. 5C, an optional waterproof seal 251 (e.g., a gasket, an O-ring,putty, caulk, etc.) may be positioned between the manhole cover 230A andthe manhole ring support 250A. The seal 251 is configured to preventwater ingress into vault 12 from between the manhole cover 230A and themanhole ring support 250A. Referring to FIG. 5A, optionally, as will bedescribed below, one or more dams 582 (see FIGS. 6A-6C) and/or one ormore moats 586 (see FIGS. 6A-6C) may be formed in the manhole ringsupport 250A, when present, and/or one or more moats 590 (see FIGS.6A-6C) may be formed in the surface 30 alongside the manhole cover 230A.While the manhole cover 230A has been illustrated as being supported bythe manhole ring support 250A, the manhole cover 230A may alternativelybe supported by alternative manhole ring supports (e.g., the manholering support 250B depicted in FIGS. 6A-6C or the manhole ring support250G depicted in FIGS. 21A, 21B, and 26) described below.

The manhole cover 230A has a top surface 232A and a bottom surface 234A.Referring to FIG. 5B, optionally, the coupling flange 332 may extenddownwardly from the bottom surface 234A. Alternatively, the couplingflange 332 may be a separate component adjacent and, optionally, coupledto the bottom surface 234A. At least one fastener F1 (e.g., a pin, ascrew, a bolt, and the like) may be used to removably couple thecoupling flange 332 to the air moving assembly 240 (see FIG. 4A). WhileFIG. 5B illustrates only the single fastener F1, more than one fastenermay be so employed. For example, three or four fasteners may be used.

Referring to FIG. 5A, the vent hole(s) 152 (see FIG. 3 ) have beenimplemented as at least one vent hole 252A and the exhaust hole(s) 153(see FIG. 3 ) have been implemented as at least one exhaust hole 253A.The vent and exhaust holes 252A and 253A extend between the top andbottom surfaces 232A and 234A and may have axes oriented in a directionsubstantially perpendicular to the surfaces 232A and 234A. In FIG. 5A,the manhole cover 230A includes only the one centrally located exhausthole 253A and only the single vent hole 252A. The vent and exhaust holes252A and 253A may be displaced (or spaced apart) from one another as faras practical so as to minimize re-entry (through the vent hole 252A) ofexhaust gases (represented by the arrows A2 in FIG. 3 ) exiting from theexhaust hole 253A.

First Alternate Embodiment of Manhole Cover

Referring to FIGS. 6A-6C, the ventilation system 210 may include analternate embodiment of a manhole cover 230B instead and in place of themanhole cover 230A (see FIGS. 4A-5B) and the manhole ring support 250B(described below) instead and in place of the manhole ring support 250A(see FIGS. 5A, 5B, 9B, and 19 ).

FIG. 6A is a top view of the manhole cover 230B resting on the manholering support 250B. Referring to FIG. 6A, the manhole cover 230B issubstantially similar to the manhole cover 230A (see FIGS. 4A-5B). Likethe manhole cover 230A, the manhole cover 230B includes top and bottomsurfaces 232B and 234B and an exhaust hole 253B substantially identicalto the exhaust hole 253A (see FIGS. 5A and 5B). However, in theembodiment illustrated, the manhole cover 230B includes vent holes 252Bthat each have an oblong lateral cross-sectional shape. Theseoblong-shaped vent holes 252B are aligned with an effective slope S1 ofthe surface 30. This shape and orientation may help keep surface water(e.g., precipitation) out of the interior 50 (see FIG. 1 ) of the vault12 (see FIGS. 1, 3-4B, 9A, 18, 19, 21A, 21B, 26A, and 32 ). The ventholes 252B are circumferentially disposed along a radial position closerto the periphery of the manhole cover 230B than the centrally locatedexhaust hole 253B.

Optionally, a plurality of the vent hole plugs 652D (see FIGS. 8A-8D,8H, 8I, and 16 ) may be inserted one each into some of the vent holes252B and/or a plurality of the vent hole plugs 652F (see FIGS. 10A, 10B,10D-10F, and 17A-17C) may be inserted one each into some of the ventholes 252B. Similarly, the exhaust hole plug 653D (see FIGS. 8A-8C, 8F,8G, 9A, 15, and 19 ) may be inserted into the exhaust hole 253B.

Optionally, as will be described below, the one or more dams 582 (seeFIGS. 6A-6C) and/or one or more moats 586 (see FIGS. 6A-6C) may beformed in the manhole ring support 250B and/or the one or more moats 590(see FIGS. 6A-6C) may be formed in the surface 30 alongside the manholecover 230B. While the manhole cover 230B has been illustrated as beingsupported by the manhole ring support 250B, the manhole cover 230B mayalternatively be supported by alternative manhole ring supports (e.g.,the manhole ring support 250A illustrated in FIGS. 5A, 5B, 9B, and 19 orthe manhole ring support 250G illustrated in FIGS. 21A, 21B, and 26 )described below.

Second Alternate Embodiment of Manhole Cover

Referring to FIG. 7 , the ventilation system 210 may include analternate embodiment of a manhole cover 230C instead and in place of themanhole cover 230A (see FIGS. 4A-5B). The manhole cover 230C isconfigured for use with the removable access cover 238 and the manifold246A.

The manhole cover 230C has a top surface 232C opposite a bottom surface234C. The manhole cover 230C includes the central access hole 236, whichextends between the top and bottom surfaces 232C and 234C. The accesshole 236 is covered by the access cover 238. In the embodimentillustrated, the access cover 238 is recessed inside the central accesshole 236 and positioned below the top surface 232C. The access cover 238rests upon a ring-shaped ledge 233 formed inside the central access hole236. One or more fasteners F2 (e.g., bolts or screws) may be used tocouple the access cover 238 to the manhole cover 230C (e.g., to theledge 233).

Both vent holes 252C and exhaust holes 253C extend between the top andbottom surfaces 232C and 234C. The vent holes 252C are arranged along afirst ring and the exhaust holes 253C are arranged along a second ringconcentric with the first ring. The second ring has a smaller radiusthan the first ring and, therefore, is positioned inside the first ring.As will be described below, the manifold 246A channels or directs theinternal air pushed by the air moving assembly 240 toward the exhaustholes 253C of the manhole cover 230C.

The manhole cover 230C may be supported by a manhole ring support (e.g.,the manhole ring support 250A, 250B, or 250G illustrated in FIGS. 5A,6A, and 21A, respectively). Optionally, a plurality of the vent holeplugs 652D (see FIGS. 8A-8D, 8H, 8I, and 16 ) may be inserted one eachinto some of the vent holes 252C and/or a plurality of the vent holeplugs 652F (see FIGS. 10A, 10B, 10D-10F, and 17A-17C) may be insertedone each into some of the vent holes 252C. Similarly, a plurality of theexhaust hole plugs 653D (see FIGS. 8A-8C, 8F, 8G, 9A, 15, and 19 ) maybe inserted one each into the exhaust holes 253C.

Third Alternate Embodiment of Manhole Cover

Referring to FIG. 8A, the ventilation system 210 may include analternate embodiment of a manhole cover 230D instead and in place of themanhole cover 230A (see FIGS. 4A-5B). The manhole cover 230D isconfigured for use with the removable access cover 238, the vent holeplugs 652D, the exhaust hole plugs 653D, and the manifold 246D(described below). The manifold 246D is used instead and in place of themanifold 246A (see FIGS. 7, 9B, and 19 ). The ventilation system 210 ispresented as an isometric view in FIG. 8A and as an exploded view inFIG. 8B. In these figures, the air moving assembly 240 is truncated forillustration purposes, but it should be understood that it may extend toany desired vertical level within the vault 12 (see FIGS. 1, 3-4B, 9A,18, 19, 21A, 21B, 26A, and 32 ). FIG. 8C is a top view of theventilation system 210. FIGS. 8F and 8H are cross-sectional views takenthrough lines 8F-8F and 8H-8H, respectively, shown in FIG. 8C, and showa sub-assembly of the manhole cover 230D and the manifold 246D.

The manhole cover 230D is substantially similar to the manhole cover230C (see FIG. 7 ). Referring to FIG. 8F, the manhole cover 230D has atop surface 232D opposite a bottom surface 234D. The manhole cover 230Dincludes the central access hole 236, which extends between the top andbottom surfaces 232D and 234D. The access hole 236 is covered by theremovable access cover 238. In the embodiment illustrated, the accesscover 238 is coupled to the manhole cover 230D by the fastener(s) F2(e.g., bolts or screws).

Referring to FIG. 8E, the vent hole(s) 152 (see FIG. 3 ) have beenimplemented as vent hole(s) 252D and the exhaust hole(s) 153 (see FIG. 3) have been implemented as exhaust holes 253D. Both the vent holes 252Dand the exhaust holes 253D extend between the top and bottom surfaces232D and 234D (see FIG. 8F). The vent holes 252D are arranged along afirst ring and the exhaust holes 253D are arranged along a second ringconcentric with the first ring. In the embodiment illustrated, theexhaust holes 253D are each elongated and each extends radiallyoutwardly at least partially between a different pair of adjacent ventholes 252D. Thus, the exhaust holes 253D and the vent holes 252D overlapradially.

Unlike the manhole cover 230C (see FIG. 7 ), the manhole cover 230Dincludes elevation dams or walls 235D that at least partially definewater channels or raceways 237D. The elevation walls 235D partiallysurround each vent hole 252D and each exhaust hole 253D. The elevationwalls 235D extend upwardly and may optionally extend upwardly beyond thesurface 30 (see FIGS. 1, 3-6C, 9A, 9B, 18, 19, 21A, 26A, and 32 ). Theelevation walls 235D and the raceways 237D allow surface water (e.g.,precipitation such as rain and melted snow) to runoff the manhole cover230D and reduce or minimize the flow thereof into the vent and exhaustholes 252D and 253D. The elevation walls 235D may be aligned with agrade (represented by an arrow S2 in FIG. 6A) of the surface 30.

State and local regulations typically limit the height of surfacefeatures like the elevation walls 235D. For this reason, the elevationwalls 235D should generally be no taller than about ⅛ inches to about3/16 inches. The raceways 237D can also be used to collect surface waterand/or direct surface water into hole-free areas of the manhole cover230D.

Referring to FIG. 8H, the vent hole plugs 652D (described below) mayalso help prevent precipitation (e.g., rain and snow) from entering thevault 12 (see FIGS. 1, 3-4B, 9A, 18, 19, 21A, 21B, 26A, and 32 ) via thevent holes 252D. Similarly, referring to FIG. 8F, the exhaust hole plugs653D (described below) may also help prevent precipitation (e.g., rainand snow) from entering the vault 12 (see FIGS. 1, 3-4B, 9A, 18, 19,21A, 21B, 26A, and 32 ) via the exhaust holes 253D. For example,referring to FIG. 8C, if the elevation walls 235D are overwhelmed by aheavy flow of water, the vent and exhaust hole plugs 252D and 253D helpreduce direct flow of water into the vault 12 (see FIGS. 1, 3-4B, 9A,18, 19, 21A, 21B, 26A, and 32 ).

Optionally, the manhole cover 230D may be supported by a manhole ringsupport (e.g., the manhole ring support 250A, 250B, or 250G illustratedin FIGS. 5A, 6A, and 21A, respectively). As will be described below, theone or more dams 582 (see FIGS. 6A-6C) and/or one or more moats 586 (seeFIGS. 6A-6C) may be formed in the manhole ring support and/or the one ormore moats 590 (see FIGS. 6A-6C) may be formed in the surface 30alongside the manhole cover 230D.

Fourth Alternate Embodiment of Manhole Cover

Referring to FIGS. 9A and 9B, the ventilation system 210 may include analternate embodiment of a manhole cover 230E instead and in place of themanhole cover 230A (see FIGS. 4A-5B). Referring to FIG. 9B, the manholecover 230E is configured for use with the manhole ring support 250A, theexhaust hole plugs 653D, and the manifold 246A.

Referring to FIG. 9B, the manhole cover 230E includes exhaust holes 253Ethat extend between top and bottom surfaces 232E and 234E. The manifold246A is coupled to the bottom surface 234E, and this combination restson the ledge 254A of the manhole ring support 250A. The manifold 246Aprovides fluid communication between the air moving assembly 240 and theexhaust holes 253E.

Unlike other embodiments described above, the manhole cover 230E omitsvent holes. Instead, portions of the external atmosphere 102 (see FIG. 3) may enter the vault 12 via other means (e.g., through a gap definedbetween the manhole cover 230E and the manhole ring support 250A,through the vent stack 132 illustrated in FIG. 3 , through the conduits20A-20C depicted in FIG. 1 , and the like).

Optionally, the one or more dams 582 (see FIGS. 6A-6C) and/or one ormore moats 586 (see FIGS. 6A-6C) may be formed in the manhole ringsupport 250A and/or the one or more moats 590 (see FIGS. 6A-6C) may beformed in the surface 30 alongside the manhole cover 230E.

Fifth Alternate Embodiment of Manhole Cover

Referring to FIGS. 10A-10F, the ventilation system 210 (see FIGS. 4A-5B,6A, 7-8C, 9A, and 9B) may include an alternate embodiment of a manholecover 230F instead and in place of the manhole cover 230A (see FIGS.4A-5B). Referring to FIG. 10A, the manhole cover 230F is configured foruse with an exhaust passage cap 280 and the vent hole plugs 652F(described below). Optionally, the coupling flange 332 (see FIGS. 5B, 7,8B, 8F, 8H, and 9B) may be used to couple the manhole cover 230F to theair moving assembly 240 (see FIGS. 4A, 4B, 7-8B, 9A, 9B, and 18 ).Together, the manhole cover 230F, the exhaust passage cap 280, and thevent hole plugs 652F form a manhole cover assembly 290.

Referring to FIG. 10D, the manhole cover 230F has a top surface 232Fopposite a bottom surface 234F. The manhole cover 230F includes a singleexhaust hole 253F that also functions as the access hole 236 (see FIGS.7, 8B, 8E, 8F, and 8H). The exhaust hole 253F is covered by the exhaustpassage cap 280, which provides functionality similar to that of theaccess cover 238 (see FIGS. 7, 8A-8C, 8F, and 8H). In the embodimentillustrated, the exhaust passage cap 280 is coupled to the manhole cover230F by one or more fasteners F3 (e.g., bolts or screws).

Referring to FIG. 10A, the manhole cover 230F has a recessed portion 288surrounding the exhaust hole 253F. The recessed portion 288 includesupwardly extending support walls or ribs 292 that extend radiallyoutwardly from the exhaust hole 253F under the exhaust passage cap 280.The ribs 292 are rack-like members configured to support the exhaustpassage cap 280, which is fastened thereto by the fastener(s) F3.Referring to FIG. 10C, the ribs 292 are corrugated along or includegrooves 293′ (see FIG. 10D) formed in their upper edge surfaces 293.

Recesses or channels 294 are defined between adjacent ones of the ribs292. Air exiting the air moving assembly 240 (see FIGS. 4A, 4B, 7-8B,9A, 9B, and 18 ) flows out of the exhaust hole 253F, into the channels294, and out openings 295 (see FIG. 10B) defined between the peripheraledge of the exhaust passage cap 280 and the manhole cover 230F. Thus,the channels 294 provide functionality to similar to that provided bythe manifold 246A (see FIGS. 7, 9B, and 19 ). Accordingly, in thisembodiment, the exhaust hole 253F (see FIG. 10C) provides the samefunctionality as a manifold port 330A (described below and illustratedin FIGS. 7 and 9B).

Referring to FIG. 10D, vent holes 252F extend between the top and bottomsurfaces 232F and 234F. The vent holes 252F are arranged along a firstring that is spaced apart from and surrounds the exhaust hole 253F. Inthis embodiment, the vent holes 252F are round and each configured toreceive a different one of the vent hole plugs 652F. The vent hole plugs652F may be characterized as being disposed near the periphery of themanhole cover 230F. Referring to FIG. 10F, in the embodimentillustrated, the vent hole plugs 652F are recessed and each rests upon aring-shaped or annular ledge 296 that is positioned below the topsurface 232F of the manhole cover 230F and surrounds the vent hole 252Finto which the vent hole plug has been inserted.

In FIG. 10C, the exhaust passage cap 280 (see FIGS. 10A, 10B, 10D, and10E) and round vent hole plugs 652F (see FIGS. 10A, 10B, 10D-10F, and17A-17C) have been removed, exposing the ribs 292 and the vent holes252F, respectively. The manhole cover 230F includes elevation walls 298that partially or fully surround each of the vent and/or exhaust holes252F and 253F and a circular elevation wall 299 that surrounds therecessed portion 288. The circular elevation wall 299 is configured tolimit ingress of liquids and solids into the channels 294 via theopenings 295 (see FIG. 10B). The elevation walls 298 (which typicallyextend about ⅛ inch to about ¼ inch above the top surface 232F) maylimit ingress of water and facilitate runoff thereof. Experimentssimulating surface run-off from “heavy rain” conditions have shown thatsuch elevation walls help to limit the amount of water that can enter agiven hole in the manhole cover 230F, particularly when, as illustratedin FIG. 10F, the interior periphery of the elevation wall 298 isdisplaced slightly (e.g., by the ledge 296) from the periphery of thecorresponding hole (e.g., the vent hole 252F). Referring to FIG. 10F anannular area of the ledge 296 (i.e., between the inner periphery of theelevation wall 298 and the periphery of the round vent hole 252F) istwice the cross-sectional area of the round vent hole 252F.

Additionally, experiments suggest that certain hole shapes are better atkeeping water out. For example, star-shaped holes (e.g., a six-pointedstar) and oval/oblong-shaped holes (e.g., the exhaust holes 253F and thevent holes 252F shown in FIG. 8E) were found to be superior to roundholes, in the latter case only when the water flow direction was alongthe long axis of the oval.

Referring to FIGS. 10E and 10G, the exhaust passage cap 280, hasconcentric corrugations or ridges 282 (see isometric view of the exhaustpassage cap 280 in FIG. 10G) formed on its underside and configured tobe received within and mate with the grooves 293′ (see FIG. 10D) formedin the upper edge surfaces 293 (see FIG. 10C) of the ribs 292 (see FIG.10C).

Referring to FIG. 10E, the channels 294 defined between the manholecover 230F and the exhaust passage cap 280 function as exhaust passagesthat are in fluid communication with both the exhaust hole 253F and theopenings 295.

Optionally, the manhole cover 230F may be supported by a manhole ringsupport (e.g., one of the manhole ring supports 250A, 250B, or 250Gillustrated in FIGS. 5A, 6A, and 21A, respectively). Optionally, the oneor more dams 582 (see FIGS. 6A-6C) and/or one or more moats 586 (seeFIGS. 6A-6C) may be formed in the manhole ring support and/or the one ormore moats 590 (see FIGS. 6A-6C) may be formed in the surface 30alongside the manhole cover 230F.

Air Moving Assembly

Referring to FIG. 4A, as mentioned above, the ventilation system 210includes the air moving assembly 240. The air moving assembly 240includes a ventilation conduit or pipe 400 and an air moving device orventilator 410. Optionally, the air moving assembly 240 may include oneof the optional manifolds 246A (see FIGS. 7, 9B, and 19 ), 246D (seeFIGS. 8A, 8B, 8D, 8F, and 8H), and 460 (see FIGS. 11A-11C) and/or anoptional float assembly 412 (see FIG. 12 ). As will be described infurther detail below, the ventilator 410 may be implemented as anin-line heater 500 (see FIGS. 8A, 8B, 9A, and 13A-13C), an in-lineblower or fan 550 (see FIGS. 14A-14C), or a ventilator assembly 1100(see FIGS. 27 and 30-32 ). By way of additional non-limiting examples,the ventilator 410 may be implemented as a forced convection device, apowered bellows, a compressor, a piston pump, a piston ventilator, anin-line pump, a fan, a blower, a cartridge heater, a coil heater, or aheat-generating device configured to provide passive heating, such as atransformer, generator, compressor, and the like.

Ventilation Pipe

Referring to FIG. 3 , the term “ventilation pipe” as used herein isgiven its broadest definition and includes any hollow structure that canconvey a portion of the internal atmosphere 104 (e.g., the gaseouscomposition 106) and/or a portion of the external atmosphere 102therethrough. This terminology thus includes such elements as a tube,channel, duct, conduit, or hose and can be a separate structure, or onethat is, at least in part, incorporated into the design of the vault 12.

Referring to FIG. 4A, the ventilation pipe 400 may be positionedadjacent to the manhole cover 230A and optionally coupled thereto.Referring to FIG. 7 , in some embodiments, the manifold 246A (or themanifold 246D depicted in FIGS. 8A, 8B, 8D, 8F, and 8H, or the manifold460 depicted in FIGS. 11A-11C) is positioned between the manhole cover(e.g., the manhole cover 230C) and the ventilation pipe 400.

Referring to FIG. 5A, the ventilation pipe 400 has one or more walls 430that define an interior through-channel 432. By way of a non-limitingexample, referring to FIG. 20 , the ventilation pipe 400 may have agenerally circular cross-sectional shape with an inner diameter D1(defined by the wall(s) 430) of about 1 inch to about 12 inches. Forexample, the inner diameter D1 may be about 3 inches to about 5 inches.

Referring to FIG. 4A, the ventilation pipe 400 has a first open end 440opposite a second open end 442 with the ventilator 410 (when present)positioned therebetween. The ventilation pipe 400 may include (or beconstructed from) multiple sections. For example, referring to FIG. 4A,the ventilation pipe 400 may include sections P1 and P2. In thisimplementation, the ventilator 410 is positioned between the sections P1and P2. As shown in FIG. 8A, the section P1 may have a lower end 401with a lower flange 402 configured to be coupled to the ventilator 410.Similarly, the section P2 may have an upper end 403 with an upper flange404 configured to be coupled to the ventilator 410.

Referring to FIG. 4B, by way of another non-limiting example, theventilation pipe 400 may include one or more joints J1-J4 (e.g.,elbows), one or more substantially vertical sections V1-V4, and/or oneor more substantially horizontal sections H1 and H2. In FIG. 4B, theventilator 410 is positioned between the two vertical sections V3 and V4of the ventilation pipe 400. In such embodiments, the vertical sectionsV3 and V4 may be substantially similar to the sections P1 and P2illustrated in FIG. 4A. For example, referring to FIG. 9A, the verticalsection V3 may include a lower flange 472 (substantially identical tothe lower flange 402 illustrated in FIG. 8A) configured to be coupled tothe ventilator 410 and the vertical section V4 may include the upperflange 474 (substantially identical to the upper flange 404 illustratedin FIG. 8A) configured to be coupled to the ventilator 410.

By way of additional non-limiting examples, the ventilation pipe 400 mayinclude sections that are angled, tapered, curved, and the like.Further, different sections of the ventilation pipe 400 may havedifferent cross-sectional sizes and/or shapes.

The ventilation pipe 400 may be implemented using a flexible hose (e.g.,corrugated metal or plastic) of an appropriate diameter, with the secondopen end 442 thereof positioned as desired within the main chamber 52 ofthe vault 12. Referring to FIG. 4A, the ventilation pipe 400 may includea combination of rigid and flexible sections arranged in suitableconfigurations. For example, the ventilation pipe 400 may have avertical rigid section (e.g., the section P1) fluidly connected to themanhole cover 230A at its bottom surface 234A (or, as described below,to one of the manifolds 246A, 246D, and 460, when present). The verticalrigid section (e.g., the section P1) may be coupled (e.g., by theventilator 410) to a flexible section (e.g., the section P2) thatextends to a desired location within the main chamber 52 of the vault12. In such an embodiment, the vertical rigid section, the ventilator410 (when present), and the flexible section provide a continuous fluidpath.

Referring to FIG. 4A, the first open end 440 has at least one outlet orfirst opening 446 that is in fluid communication with the interiorthrough-channel 432 (see FIG. 5A) of the ventilation pipe 400. As shownin FIGS. 5A and 5B, the first open end 440 of the ventilation pipe 400is positioned proximal to the exhaust hole 253A of the manhole cover230A (e.g., at its bottom surface 234A) such that there is fluidcommunication between the interior through-channel 432 of theventilation pipe 400 and the exhaust hole 253A (via the first opening(s)446). Although, the first open end 440 of the ventilation pipe 400 maybe in contact with the bottom surface 234A, and sealably secured theretoto provide a fluid-tight connection, it is also contemplated that theremay be a small gap between the first open end 440 of the ventilationpipe 400 and the bottom surface 234A, provided that most, and preferablyessentially all, of the portion of the internal atmosphere 104 (e.g.,the gaseous composition 106 illustrated in FIG. 3 ) being exhaustedthrough the first opening(s) 446 of the ventilation pipe 400 is alsocaused to flow through the exhaust hole 253A.

Alternatively, the first open end 440 may be positioned proximal to thevent hole 252A of the manhole cover 230A (e.g., at its bottom surface234A) such that there is fluid communication between the interiorthrough-channel 432 of the ventilation pipe 400 and the vent hole 252A(via the first opening(s) 446). In such implementations, the first openend 440 of the ventilation pipe 400 may be in contact with the bottomsurface 234A or spaced apart therefrom provided a substantial portion ofthe external atmosphere 102 (see FIG. 3 ) being drawn in through thevent hole 252A flows into the first opening(s) 446.

Referring to FIG. 4A, the second open end 442 of the ventilation pipe400 is positioned in the main chamber 52 of the vault 12. Theventilation pipe 400 has at least one intake or second opening 448 influid communication with both the internal atmosphere 104 (see FIG. 3 )and the interior through-channel 432 (see FIGS. 5A and 5B). In theembodiment illustrated, the second opening 448 is formed at or near thesecond open end 442. The second opening(s) 448 may simply include theopening of the interior through-channel 432 defined by the wall(s) 430(see FIGS. 5A, 5B, 19, and 20 ) at the second open end 442 of theventilation pipe 400.

Optionally, the second opening(s) 448 may include one or more holes(e.g., holes 449 depicted in FIG. 9A) formed in the wall(s) 430 (seeFIGS. 5A, 5B, 19, and 20 ) of the ventilation pipe 400 and locatedproximal to the second open end 442. In embodiments in which at leastsome of the second opening(s) 448 are formed in the wall(s) 430, thesecond open end 442 of the ventilation pipe 400 may be completely orpartially closed (or blocked). Those of the second opening(s) 448 formedin the wall(s) 430 may be generally circular. In such embodiments, thesecond opening(s) 448 may have a diameter that is less than apredetermined percentage (e.g., about 5% or about 10%) of the innerdiameter D1 (see FIG. 20 ) of the ventilation pipe 400. Referring toFIG. 20 , those of the second opening(s) 448 that extend laterallythrough one of the wall(s) 430 may be at least partially covered orblocked by a flap portion 447 (defined in one of the wall(s) 430).

Referring to FIG. 4A, the ventilation pipe 400 may be configured toposition its second open end 442 and/or at least one second opening 448at any desired vertical position or level within the vault 12. Forexample, the ventilation pipe 400 may also be configured to draw thegaseous composition 106 (see FIG. 3 ) from any desired point(s) (e.g.,lower levels of the main chamber 52) within the vault 12 using suitableconnectors (e.g., the joints J1-J4 depicted in FIG. 4B) and extensions(e.g., the sections P1 and P2, the horizontal sections H1-H2, and/or thevertical sections V1-V4). By way of non-limiting examples, right-angleelbows in combination with straight pipe sections may be used.

Multiple second openings 448 may be positioned at vertical levels justabove the floor 58 (e.g., about ½ foot above the floor 58). As furtherdescribed below, it has been found that when all of the second openings448 of the ventilation pipe 400 are positioned more than 3 feet abovethe floor 58, the removal of heavier-than-air gases and vapors issignificantly reduced. To avoid this limitation, at least one secondopening 448 may be positioned about 3 feet or less above the floor 58 todraw heavier-than-air gases from the lower regions of the vault 12. Forexample, the ventilation pipe 400 may extend into the main chamber 52such that at least one second opening 448 is positioned about 2 feet orless above the floor 58. By way of a non-limiting example, at least onesecond opening 448 may be positioned about a half foot above the floor58.

In implementations that include only a single second opening, the secondopening 448 may be positioned at a location between about one foot abovethe floor 58 and substantially at floor level. When the second opening448 is substantially at floor level, a sufficient gap may be providedbetween the second opening 448 and the floor 58 to allow air to flowinto and/or out of the second opening 448.

Furthermore, portions of the internal atmosphere 104 (see FIG. 3 ) maybe simultaneously drawn from multiple vertical and/or horizontal siteswithin the main chamber 52 of the vault 12. For example, the secondopening(s) 448 may include the plurality of holes 449 (see FIG. 9A)provided along at least a portion of the ventilation pipe 400 and thesecond open end 442 may be partially or entirely blocked.

The second openings 448 may also be positioned such that the ventilationsystem 210 functions when the water 80 (see FIG. 3 ) is in the mainchamber 52 (e.g., the main chamber 52 is flooded). For example, multiplesecond openings 448 may be positioned along a portion (e.g., the sectionP2, the section V4, and the like) of the length of the ventilation pipe400 so that if the main chamber 52 is partially flooded due toparticularly heavy precipitation, the ventilation pipe 400 will draw thegaseous composition 106 (see FIG. 3 ) through those of the secondopenings 448 that are positioned above the water level and maintaineffective exhaust of the undesired gaseous composition. Alternatively,the ventilation pipe 400 may deliver a portion of the externalatmosphere 102 (see FIG. 3 ) into the main chamber 52 through those ofthe second openings 448 that are positioned above the water level tothereby maintain effective ventilation of the vault 12.

The second openings 448 may have different, graduated, or varying sizes(and/or shapes) and may be positioned along at least a portion of thelength of the ventilation pipe 400 to optimize the exhaust of thegaseous composition 106 (see FIG. 3 ) and/or reduce (or minimize) airstagnation in the main chamber 52 of the vault 12. In such embodiments,and the second open end 442 may be partially or entirely blocked. Thearea of such second openings 448 may vary with height so that there isless open area near the upper first open end 440 than near the lowersecond open end 442 of the ventilation pipe 400. For example, FIG. 9Aillustrates an implementation of the ventilation pipe 400 similar tothat depicted in FIG. 4B, except, in FIG. 9A, the ventilation pipe 400includes multiple second openings 448 that are graduated. As shown inFIG. 9A, those of the second openings 448 formed nearer the lower secondopen end 442 have greater open areas (e.g., larger diameters) than thoseof the second openings 448 formed nearer the upper first open end 440.

Of course, one of ordinary skill in the art will appreciate that theabove exemplary values for placement of the second opening(s) 448 of theventilation pipe 400 may vary according to one or more factors, e.g.,vault dimensions, nature of gases likely to be encountered,environmental parameters, floor profile, vault shape, and equipmentlocated within the vault. One of ordinary skill in the art can determinesuitable (e.g., optimal) placement of the second opening(s) 448 for agiven situation by applying ordinary skill in the art to the presentteachings (e.g., by following the guidelines described in theExperimental section, below).

Although, in FIGS. 4A and 4B, the ventilation pipe 400 is shown withoutsupport within the vault 12, the ventilation pipe 400 may be held inplace by a bracket, mechanical arm, chain, cable, or other suitablesupport means, particularly when the ventilation pipe 400 is notmechanically attached to the manhole cover 230A. The ventilation pipe400 may be held in place near the bottom surface 234A (see FIGS. 5A and5B) of the manhole cover 230A to provide sufficient clearing of thegaseous composition 106 (see FIG. 3 ) composition within the vault 12.Alternatively, these components may be mechanically coupled togethersuch that they may be lifted from the vault 12 together as a unit. Thisunit can be suspended from a tripod or like portable structure outsidethe vault 12 until the needed work is completed. If the ventilation pipe400 is flexible or has a flexible section (e.g., the section P2), suchflexible portions may be collapsed to a relatively short length (e.g.,using a line attached to a hook) and lifted out of the vault 12 alongwith the manhole cover 230A.

Referring to FIG. 4B, to keep the ventilation pipe 400 out of the way ofworkers (e.g., the worker 61 depicted in FIGS. 1 and 3 ) entering thevault 12, the ventilation pipe 400 may hug (and be fastened to) at leastone of the sidewall(s) 54, the ceiling 56, and at least one of thewall(s) 64 of the neck 60. Referring to FIG. 5B, an L-shaped section (ora Z-shaped section if desired) of the ventilation pipe 400 (e.g., asubassembly of the joints J1 and J2 and the horizontal section H1) maybe disconnected from the manhole cover 230A by reaching in from thesurface 30 through the central exhaust hole 253A (or the access hole 236included in some embodiments and depicted in FIGS. 7, 8B, 8E, 8F, and8H) and removing the fastener(s) F1 (see FIG. 5B). Then, thisdisconnected section may be swung out of the way, or lifted out of thevault 12 completely, to allow access to the main chamber 52 (e.g., via aladder, not shown).

The ventilation pipe 400 may be fabricated from a rigid plastic or metaland may be assembled from pipe segments constructed from such materials.FIGS. 9A and 9B depict an exemplary implementation of the ventilationpipe 400 that includes the joints J1-J4, the vertical sections V1-V4,and the horizontal sections H1-H2. In this embodiment, the joints J1-J4,the vertical sections V1-V4, and the horizontal sections H1-H2 may eachbe constructed from fiberglass pipe or polyvinyl chloride (“PVC”)plastic pipe (e.g., 4 inch schedule 40 PVC pipe). One or more of thejoints J1-J4 may be implemented as a 90° PVC elbow.

Referring to FIG. 9B, in this implementation, the joints J1 and J2 andthe horizontal section H1 define a Z-shaped duct 470. Referring to FIG.9A, the Z-shaped duct 470 and/or the vertical section V1 is/are attachedto one of the sidewall(s) 54 of the main chamber 52 or one of thewall(s) 64 of the neck 60 (e.g., by brackets, not shown). The lowervertical section V4 is mounted near floor level on a support block 462.The support block 462 may partially or completely block or close thesecond open end 442 of the ventilation pipe 400. As mentioned above, thesecond openings 448 may include the holes 449 that are drilled orotherwise formed in the wall(s) 430 of the ventilation pipe 400 near itslower second open end 442. In the embodiment illustrated in FIG. 9A, thesecond openings 448 implemented by the holes 449 have varying diametersthat progressively decrease in size as the height above the supportblock 462 increases, to provide intake paths for the internal atmosphere104 (see FIG. 3 ) and/or exit paths for the external atmosphere 102 (seeFIG. 3 ). As discussed above, with such an arrangement, exhaust of gasis still possible even if the main chamber 52 of the vault 12 ispartially flooded provided some of the second openings 448 remain abovethe high water mark.

The ventilator 410 is mounted vertically along one of the sidewall(s) 54of the main chamber 52 as near to the manhole 62 as possible and withintwo feet of the ceiling 56 using commercially available pipe mountingbrackets (not shown). An upper end 471 of the lower vertical section V4has an upper flange 474 (substantially identical to the upper flange 404illustrated in FIG. 8B) that is connected to a lower flange 532 of thein-line heater 500 or, alternatively, to a lower flange 554 of thein-line fan 550 illustrated in FIGS. 14A-14C. Referring to FIG. 9A, afirst ceramic fiber mat gasket (not shown) may be placed between theseflanges whereat the ventilator 410 (e.g., the heater 500 illustrated inFIGS. 8A, 8B, 9A, and 13A-13C or the in-line fan 550 illustrated inFIGS. 14A-14C) is connected to the vertical section V4.

The horizontal section H2 is suspended from the ceiling 56 by pipehangers (not shown) which allow some movement to accommodate thermalexpansion. The joint J4 is positioned at a first end 476 of thehorizontal section H2 and connects the horizontal section H2 to thevertical section V3. A lower end 478 of the vertical section V3 has alower flange (substantially identical to the lower flange 402illustrated in FIG. 8B) that is connected to an upper flange 531 of theinline heater 500 or, alternatively, to an upper flange 552 of thein-line fan 550 illustrated in FIGS. 14A-14C. Referring to FIG. 9A, asecond ceramic fiber mat gasket (not shown) may be placed between theseflanges whereat the ventilator 410 (e.g., the heater 500 illustrated inFIGS. 8A, 8B, 9A, and 13A-13C or the in-line fan 550 illustrated inFIGS. 14A-14C) is connected to the vertical section V3. In embodimentsin which the ventilator 410 has been implemented as the heater 500 (seeFIGS. 8A, 8B, 9A, and 13A-13C), the first and second gaskets thermallyisolate the in-line heater 500 from direct contact with the horizontaland vertical sections H2, V3, and V4, which could be damaged by the hightemperature. The in-line heater 500 is also wrapped with insulation (notshown) to insulate it from the internal atmosphere 104 (see FIG. 3 )inside the vault 12 and concentrate heat in the center of the heater500, where it will promote upward gas flow within the ventilation pipe400.

The joint J3 is positioned at a second end 477 of the horizontal sectionH2. The cross-sectional profile of the joint J3 transitions fromcircular, where it is connected to the second end 477 of the horizontalsection H2, to rectangular, where it is connected to the short verticalsection V2, which has a rectangular (flattened) cross-sectional shape.Referring to FIG. 9B, the short vertical section V2 hugs and may beattached to one of the wall(s) 64 of the neck 60, thereby minimallyobstructing this narrow passageway. The top of the short verticalsection V2 is releasably inserted into a first end 480 of the Z-shapedduct 470. The first end 480 has a rectangular cross-sectional shape thathas slightly larger rectangular dimensions to accommodate the top of theshort vertical section V2 in a male/female engagement (e.g., a taperjoint).

A second end 482 of the Z-shaped duct 470 is positioned substantially atthe center of the neck 60, in alignment with the center of the manholecover 230E, and transitions from a (horizontal) rectangularcross-sectional shape to a (vertical) conical opening which can matewith (e.g., receive) a tapered lower end 486 of the coupling verticalsection V1, again in a male/female engagement (taper joint).

The coupling vertical section V1 releasably connects the manifold 246A(coupled to the bottom surface 234E of the manhole cover 230E) with theZ-shaped duct 470 to place the exhaust holes 253E in the manhole cover230E in fluid communication with the aforementioned series of components(i.e., the manifold 246A, the Z-shaped duct 470, the vertical sectionV2, the horizontal section H2, the vertical section V3, the ventilator410, the joint J3, the joint J4, and the vertical section V4).

Referring to FIG. 9B, an upper flanged end 488 of the coupling verticalsection V1 extends into the manifold 246A through the port 330A. Theupper flanged end 488 has a flange 489 that prevents the verticalsection V1 from falling through the port 330A of the manifold 246A. Thecoupling vertical section V1 may be fitted with a cross-piece handle(not shown) at or near its upper flanged end 488 to facilitate liftingthe vertical section V1 out of the port 330A.

By way of yet another exemplary implementation, referring to FIG. 4B,when a completely new manhole vault is being installed, the ventilationpipe 400 may optionally be integrated directly into one or more of thesidewall(s) 54 of the vault 12 and appropriately plumbed to the manholecover 230A (or one of the manhole covers 230B-230G shown in FIGS. 6A, 7,8A, 9B, 10A, and 22A, respectively) or the vent stack 132 (see FIGS. 3and 18 ).

Optional Manifold

Referring to FIG. 7 , when, as in the manhole cover 230C, there aremultiple exhaust holes (e.g., the exhaust holes 253C), the optionalmanifold 246A (or the manifold 246D depicted in FIGS. 8A, 8B, 8D, 8F,and 8H or the manifold 460 depicted in FIGS. 11A-11C) may be used tochannel flow from the first opening 446 of the ventilation pipe 400 intothe multiple exhaust holes. Alternatively, referring to FIG. 3 , whenthere are multiple vent holes 152, one of the optional manifolds 246A,246D, or 460 may be used to channel flow from the multiple vent holesinto the first opening 446 of the ventilation pipe 400.

Each of the manhole covers 230C-230E (see FIGS. 7, 8A, and 9B,respectively) includes multiple exhaust holes. As mentioned above, themanhole covers 230C and 230E are each configured for use with themanifold 246A, and the manhole cover 230D is configured for use with themanifold 246D. While the manhole cover 230F includes multiple exhaustholes (the openings 295 illustrated in FIGS. 10B and 10E), as explainedabove, a manifold like the manifold 246A is not necessary to channel theflow from the first opening 446 of the ventilation pipe 400 into theexhaust hole 253F and out the openings 295.

Referring to FIG. 7 , the manifold 246A is positionable between theupper first open end 440 of the ventilation pipe 400 and the manholecover 230C (or the manhole cover 230E illustrated in FIGS. 9A and 9B).The manifold 246A has a base portion 452 and one or more peripheralsidewalls 454 that extend upwardly from the base portion 452. The baseportion 452 and the peripheral sidewall(s) 454 define an upwardlyopening internal cavity 456. The manifold 246A may be positionedproximate to the bottom surface 234C of the manhole cover 230C (or thebottom surface 234E of the manhole cover 230E). For example, upperedge(s) 458 of the peripheral sidewall(s) 454 may be positioned againstthe bottom surface 234C of the manhole cover 230C (or the bottom surface234E of the manhole cover 230E) and optionally sealed thereagainst.

The manifold 246A includes the port 330A, which is formed in the baseportion 452. The port 330A is configured to receive the flow from thefirst opening 446 of the ventilation pipe 400 into the internal cavity456. The manifold 246A is configured to provide fluid communication(through the internal cavity 456) between the port 330A and all of theexhaust holes 253C (or the exhaust holes 253E illustrated in FIG. 9B).Alternatively, the port 330A may be configured to receive airflow fromthe internal cavity 456. In such implementations, the manifold 246A isconfigured to provide fluid communication (through the internal cavity456) between the port 330A and the vent holes 252C.

Although, in FIG. 9A, the ventilation pipe 400 is shown without supportwithin the vault 12, as mentioned above, the ventilation pipe 400 may beheld in place by a bracket, mechanical arm, chain, cable, or othersuitable support means, particularly when the ventilation pipe 400 isnot mechanically attached to the manifold 246A. On the other hand,referring to FIG. 9B, the port 330A may be coupled to the ventilationpipe 400, either directly or with the aid of the coupling flange 332.The coupling flange 332 may be a separate component or formed in thebottom of the manifold 246A. The manifold 246A may be sealably attachedto the bottom surface 234C of the manhole cover 230C, or at least incontact with it, directly or via a gasket (not shown). Similarly, themanifold 246A may be sealably attached to the bottom surface 234E of themanhole cover 230E, or at least in contact with it, directly or via agasket (not shown).

When the manhole cover 230C (or the manhole cover 230E), the manifold246A, and the ventilation pipe 400 are coupled together, the worker 61(see FIGS. 1 and 3 ) may lift this triad from the manhole 62 (see FIG. 1) as one unit before servicing/entering the vault 12. This unit can besuspended from a tripod or like portable structure (not shown) outsidethe vault 12 until the needed work is completed. If the ventilation pipe400 is flexible or collapsible, it can be collapsed to a relativelyshort length (e.g., using a line attached to a hook) and lifted out ofthe vault 12 along with the manifold 246A and the manhole cover 230C (orthe manhole cover 230E).

Alternatively, this triad of components may be releasably coupledtogether to allow removal of only the manhole cover 230C (or the manholecover 230E), or the combination of the manifold 246A and the attachedmanhole cover 230C (or the manhole cover 230E), while leaving theventilation pipe 400 in the vault 12. An example of such an arrangementis shown in FIG. 7 . FIG. 7 illustrates an embodiment in which thecoupling flange 332 is fastened (e.g., bolted) or otherwise attached to(e.g., formed in the bottom of) the manifold 246A, which is in turnattached (e.g., by welding or brazing) to the manhole cover 230C. Atleast one fastener F1 (e.g., a flange pin) may be inserted into andthrough aligned holes 450 formed in one of the wall(s) 430 of theventilation pipe 400 and the coupling flange 332 to hold the ventilationpipe 400 in place. While FIG. 7 illustrates only the single fastener F1,more than one fastener (or screw) may be so employed. For example, threeor four fasteners may be used.

Before the worker 61 (see FIGS. 1 and 3 ) enters the vault 12 (see FIGS.1, 3-4B, 9A, 18, 19, 21A, 21B, 26A, and 32 ), the worker 61 removes theaccess cover 238 (e.g., by removing the fasteners F2) to expose theaccess hole 236. Then, the worker 61 removes the fastener(s) F1 torelease the ventilation pipe 400 from the manifold 246A. This allows theworker 61 to lift the manhole cover 230C, along with manifold 246A andthe coupling flange 332 out of the manhole 62 (see FIG. 1 ) while theventilation pipe 400 remains in place within the vault 12. Theventilation pipe 400 may be suspended or held by a bracket, chain, orcable attached to at least one of the sidewall(s) 54 or the ceiling 56(see FIGS. 1, 4A, 4B, 9A, 18, and 19 ) of the vault 12. Such asuspension means may be capable of being moved (e.g., swung) out of theway or removed by reaching in from the surface 30 (see FIGS. 1, 3-6C,9A, 9B, 18, 19, 21A, 26A, and 32 ) to facilitate entry to the vault 12.

Other coupling means known in the art for releasably connecting theventilation pipe 400 to the subassembly formed by the manifold 246A andthe manhole cover 230C (or the manhole cover 230E) may be substitutedfor the coupling flange 332 and the fastener(s) F1. For example, thesecoupling connections can be accomplished using bolted flanges, clampedflanges, hanging a (bolted) flange from a ledge in or on the manholecover 230C (or the manhole cover 230E), magnetic coupling, hangers andhooks mating with holes or tabs in the ventilation pipe 400,spring-loaded clips, a rotating lock mechanism similar to a window sashlock, a swinging lock mechanism similar to a suitcase lock, or rotatingtabs below the cover with a key inserted from the top of the cover (apivot latch or pivot lock). Additional examples of suitable couplingmeans include a threaded connection that can swivel on an end of theventilation pipe 400 or on the manhole cover 230C (or the manhole cover230E) and has an internal securing means which can be manipulated byhand or a tool, a “bayonet” mount using a quarter or half turn lockingconnection by way of an internal handle, a snap-on/snap-off connectionincorporating protrusions and detents (e.g., a quick disconnect), and“zip” ties, cord or cable which attach features on the ventilation pipe400 to those on the manhole cover 230C (or the manhole cover 230E),among others. Of course, any such means may be configured to provide arelatively straightforward release and re-connection of the manholecover 230C (or the manhole cover 230E) and the ventilation pipe 400 fromthe surface 30 by the worker 61 (see FIGS. 1 and 3 ) who remains outsideof the vault 12 and reaches at most a hand and/or a specialized toolinto the vault 12 (via the neck 60).

The manifold 246A may be stamped or molded from a metal or plastic andattached to the manhole cover 230C (or the manhole cover 230E) by, e.g.,welding, brazing, bolting, strapping, or riveting, as appropriate.Likewise, the coupling flange 332, typically formed from steel, castiron, or plastic may be attached to the bottom surface of the manifold246A, concentric with the port 330A thereof.

First Alternate Embodiment of Optional Manifold

Referring to FIGS. 8A, 8B, 8D, 8F, and 8H, as mentioned above, themanhole cover 230D is configured for use with the manifold 246D, whichincludes the radially overlapping vent and exhaust holes 252D and 253D(see FIG. 8E).

Referring to FIG. 8B, the manifold 246D is positionable between themanhole cover 230D and the upper first open end 440 of the ventilationpipe 400. The manifold 246D has a base portion 464 and a continuousperipheral sidewall 466 that extends upwardly from the base portion 464.The base portion 464 and the peripheral sidewall 466 define an upwardlyopening internal cavity 468. Referring to FIG. 8F, the peripheralsidewall 466 is configured to extend around each of the exhaust holes253D such that each of the exhaust holes 253D is in fluid communicationwith the internal cavity 468 when the manifold 246D is adjacent thebottom surface 234D of the manhole cover 230D. For example, when anupper edge 467 of the peripheral sidewall 466 is positioned against thebottom surface 234D of the manhole cover 230D and optionally sealedthereagainst. Thus, in the embodiment shown in FIG. 8B, the manifold246D has a radially outwardly extending portion 465 (see FIG. 8D) foreach of the exhaust holes 253D (see FIGS. 8E-8G) that extends between atleast two adjacent vent holes 252D (see FIGS. 8D, 8E, 8H, and 8I). Asshown in FIG. 8H, the radially outwardly extending portions 465 (seeFIG. 8D) are positioned such that the vent holes 252D are not in fluidcommunication with the internal cavity 468 when the manifold 246D isadjacent the bottom surface 234D of the manhole cover 230D.

Referring to FIG. 8B, the manifold 246D includes a port 330D formed inthe base portion 464 that is substantially similar to the port 330A (seeFIGS. 7 and 9B) of the manifold 246A (see FIGS. 7, 9B, and 19 ). Theport 330D is configured to receive the flow from the first opening 446of the ventilation pipe 400 into the internal cavity 468. The manifold246D is configured to provide fluid communication (through the internalcavity 468) between the port 330D and all of the exhaust holes 253D (seeFIGS. 8E-8G).

Second Alternate Embodiment of Optional Manifold

Referring to FIGS. 11A-11C, the air moving assembly 240 may include asecond alternate embodiment of a manifold 460 instead and in place ofeither the manifold 246A (see FIGS. 7, 9B, and 19 ) or the manifold 246D(see FIGS. 8A, 8B, 8D, 8F, and 8H). The manifold 460 may becharacterized as having a skeletonized structure. By way of non-limitingexamples, the manifold 460 may be fabricated from aluminum or steel.

Referring to FIG. 11A, the manifold 460 has a circular rim 610 andradial support ribs 630. The circular rim 610 is configured to rest onthe ledge 254A (see FIGS. 5A, 5B, and 9B) of the ring support 250A (seeFIGS. 5A, 5B, 9B, and 19 ). The circular rim 610 is configured to besandwiched between the ledge 254A and the manhole cover 230C (see FIG. 7) or the manhole cover 230E (see FIGS. 9A and 9B).

The ribs 630 are attached to and extend radially inwardly from the rim610. The ribs 630 define two central, concentric, hexagonal structures612 and 614. The structure 612 is positioned inside the structure 614.Openings 616 are defined between adjacent ribs 630, the structure 614,and the circular rim 610. The structure 614 is positioned along andcoupled to an upper edge of a central hexagonal-shaped pan 640. By wayof a non-limiting example, the central hexagonal pan 640 may be about 4inches deep. The pan 640 has a central port 620 that is substantiallysimilar to the port 330A (see FIGS. 7 and 9B) of the manifold 246A (seeFIGS. 7, 9B, and 19 ). The port 620 may be positioned below and alignedwith the center of the structure 612. The port 620 may be aligned withand optionally coupled to the first open end 440 (see FIGS. 4A-5B, 7,8B, and 18 ) of the ventilation pipe 400 (see FIGS. 4A-5B, 7, 8A-9A, 12,18, 19, 21A, and 21B, 26A, 31, and 32 ).

For example, referring to FIG. 9B, when the manifold 460 (see FIGS.11A-11C) is used with the manhole cover 230E (instead of and in place ofthe manifold 264A) and the implementation of the ventilation pipe 400illustrated in FIG. 9B, the port 620 may receive and optionally becoupled to the second end 482 (conical opening) of Z-shaped duct 470and/or the upper flanged end 488 of the coupling vertical section V1.The ribs 630 of the manifold 460 mate with the underside of the manholecover 230E to provide at least a partial seal between the manhole cover230E and the hexagonal pan 640 such that the exhaust holes 253E are influid communication with the interior of the hexagonal pan 640. Ofcourse, only the exhaust holes 253E should be disposed within theperimeter of the pan 640 and when present, vent holes (e.g., the ventholes 252C illustrated in FIG. 7 ) should be disposed outside thisperimeter. In other words, the exhaust holes 253E and any vent holesformed in the manhole cover 230E are positioned so they do not overlapradially (e.g., all of the exhaust holes 253E are positioned closer tothe center of the manhole cover 230E than the vent holes). Thus, themanifold 460 may be used with the manhole cover 230C because the exhaustholes 253C are positioned nearer the center of the manhole cover 230Cthan the vent holes 252C. This arrangement also positions the vent holes252C to be in fluid communication with the openings 616 so that air mayflow therethrough.

The manifold 460 (see FIGS. 11A-11C) is configured to provide easyaccess to the vault 12. First, the worker 61 (see FIGS. 1 and 3 ) mayremove the manhole cover 230E, which rests on the manifold 460, byengaging a tool (such as a pick, not shown) into a closed end well(e.g., a closed end well 928 illustrated in FIG. 22A) on the manholecover 230E, lifting the manhole cover 230E off the ring support 250A,and dragging the manhole cover 230E out of the way and onto the adjacentsurface 30. Second, the worker 61 (see FIGS. 1 and 3 ) lifts thecoupling vertical section V1 out of the port 620 in the manifold 460(e.g., using the cross-piece handle, not shown). Third, the worker 61(see FIGS. 1 and 3 ) lifts the manifold 460, which rests on the ledge254A of the ring support 250A, out of the vault 12 by grasping one ormore of the ribs 630 (e.g., with hooks and cables) and places themanifold 460 on the surface 30. Fourth, the worker 61 (see FIGS. 1 and 3) lifts the Z-shaped duct 470 out of the vault 12 and places theZ-shaped duct 470 on the surface 30. At this point, the vault 12 can beentered provided all confined space procedures have been satisfied.

After any required maintenance is completed, the vault 12 is againsecured in reverse order, as follows. First, the worker 61 (see FIGS. 1and 3 ) slips the (rectangular) first end 641 of the Z-shaped duct 470into the top of vertical section V2. Second, the worker 61 (see FIGS. 1and 3 ) lowers the manifold 460 onto the ring support 250A whileensuring that the center of the port 620 is in alignment with the second(conical) end 642 of the Z-shaped duct 470. Third, the worker 61 (seeFIGS. 1 and 3 ) inserts the coupling vertical section V1 into the port620 such that the tapered end 632 of the coupling vertical section V1mates with the second (conical) end 642 of the Z-shaped duct 470. In afinal step, the worker 61 (see FIGS. 1 and 3 ) places the manhole cover230E on the manifold 460. It will be appreciated that all of the aboveoperations can be accomplished from street level (e.g., from the surface30). It should further be appreciated that the manifold 460 may beconfigured to mate with existing vented manhole covers (e.g., the ventedmanhole cover 70 illustrated in FIG. 2 ) to create zones of exhaustholes and vent holes with no, or only minimal, modification of theexisting manhole cover.

Optional Float Assembly

As mentioned above, the water 80 (see FIG. 3 ) may at least partiallyfill the main chamber 52 and block one or more of the second opening(s)448. One method of avoiding this problem is to position the secondopenings 448 at multiple locations along the ventilation pipe 400. Inthis manner, the likelihood that all of the second openings 448 will beblocked (e.g., submerged in the water 80) is significantly reduced.

Referring to FIG. 12 , the float assembly 412 may be used to maintainventilation (e.g., exhaust) during a flooding event. The assembly 412includes a flange 680, a flexible cylindrical bellows 682, a floatsubassembly 684, and a support block 686. The support block 686 may besubstantially similar to the support block 462 depicted in FIG. 9A andfixed mounted to the floor 58.

Referring to FIG. 12 , the flange 680 may be fixedly mounted to theventilation pipe 400, the ventilator 410 (see FIGS. 4A, 4B, 8A, 8B, 18,21A, 21B, and 26), and/or the ceiling 56 (see FIGS. 1, 4A, 4B, 9A, 18,and 19 ). The ventilation pipe 400 extends between the flange 680 andthe support block 686. As shown in FIG. 12 , the ventilation pipe 400passes through the bellows 682. The second open end 442 of theventilation pipe 400 rests on the support block 686 and is partiallycovered with the bellows 682. The bellows 682 may be characterized asbeing a longitudinally compressible sleeve that surrounds a portion ofthe ventilation pipe 400 near the second open end 442. One or moresecond openings 448 (formed in the wall(s) 430) of the ventilation pipe400 are positioned within the bellows 682. The bellows 682 extendsbetween the flange 680 and the float subassembly 684. The bellows 682has an upper end 688 that is attached to the flange 680 and a lower end689 attached to the float subassembly 684.

The internal atmosphere 104 (see FIG. 3 ) may flow into the bellows 682through its lower end 689 but is prevented from entering the upper end688 of the bellows 682. Thus, the bellows 682 restricts access to thesecond opening(s) 448 inside the bellows. Specifically, only portions ofthe internal atmosphere 104 (see FIG. 3 ) entering the bellows 682through its lower end 689 may reach the second opening(s) 448 within thebellows 682.

The float subassembly 684 includes a plurality of individual spacedapart floats 690 arranged circumferentially around the ventilation pipe400. Interstitial spaces or openings 692 are defined between adjacentones of the floats 690. As the level of the water 80 in the vault 12rises, the float subassembly 684 rises correspondingly and compressesthe bellows 682. In this embodiment, the second open end 442 of theventilation pipe 400 remains stationary as the float subassembly 684rises along the ventilation pipe 400. A portion of the internalatmosphere 104 (e.g., the gaseous composition 106 illustrated in FIG. 3) may be removed from the vault 12 by the second opening(s) 448positioned within the bellows 682. Portions of the internal atmosphere104 may flow between the spaced apart floats 690 (through the openings692), and upwardly between the bellows 682 and the ventilation pipe 400.Then, those portions of the internal atmosphere 104 may enter theventilation pipe 400 via the second openings 448 positioned inside thebellows 682. Variations of the above arrangement in which the bellows682 includes openings (not shown), formed either in the upper portion ofthe bellows 682 itself or in the structure which connects the upper end688 of the bellows 682 to the ventilation pipe 400, are also possible.In either case, the bellows 682 expands and contracts in lengthaccording to the prevailing water level, and the portion of the internalatmosphere 104 (see FIG. 3 ) entering the bellows 682 is drawn throughthe ventilation pipe 400 by the ventilator 410 (see FIGS. 4A, 4B, 8A,8B, 18, 21A, 21B, and 26 ) which may be in-line with the ventilationpipe 400.

The float assembly 412 allows only air that flows between the floats 690(through the openings 692) to enter the bellows 682 and the secondopenings 448 positioned inside the bellows 682. Thus, the level of theopenings 692 is an effective intake level that is determined by thelevel of the water 80. In this manner, the float assembly 412 may beused to automatically adjust the height of the effective intake level soas to maintain it above the level of the water 80. Further, the openings692 may be positioned such that they are at a predetermined distanceabove the water 80. This arrangement helps ensure the internalatmosphere 104 (see FIG. 3 ) enters the ventilation pipe 400 at or nearthe surface level of the water 80 (see FIGS. 3 and 19 ), when the wateris present. On the other hand, the portion of the internal atmosphere104 (see FIG. 3 ) enters the ventilation pipe 400 at or near the floor58, when the water 80 is not present inside the vault 12.

By way of a non-limiting example, the float assembly 412 could beinstalled on the vertical section V4 shown in FIGS. 4B and 9A, or thesection P2 shown in FIGS. 4A, 8A, and 21A.

Ventilator

Referring to FIGS. 4A and 4B, the ventilator 410 may cause a portion ofthe internal atmosphere 104 (e.g., the gaseous composition 106illustrated in FIG. 3 ) within the main chamber 52 of the vault 12 toflow in a generally upward direction through the ventilation pipe 400and eventually exit to the external atmosphere 102 through the exhausthole 253A in the manhole cover 230A. Alternatively or additionally, theventilator 410 may cause a portion of the external atmosphere 102 (seeFIG. 3 ) to flow in a generally downward direction into the main chamber52 of the vault 12 through the ventilation pipe 400. Thus, theventilator 410 is a fluid conveying means for transferring at least aportion of the internal atmosphere 104 out of the vault 12 and/ortransferring at least a portion of the external atmosphere 102 into ofthe vault 12. As discussed below, it has been found thatheavier-than-air gases or vapors are not effectively exhausted from thevault 12 without the benefit of such a ventilator when there is noprevailing wind sweeping over the top surface 232A (see FIGS. 5A and 5B)of the manhole cover 230A.

As mentioned above, the ventilator 410 may be implemented as the in-lineheater 500 (see FIGS. 8A, 8B, 9A, and 13A-13C), the in-line blower orfan 550 (see FIGS. 14A-14C), or the ventilator assembly 1100 (see FIGS.27 and 30-32 ). By way of additional non-limiting examples, theventilator 410 may be implemented as a forced convection device, apowered bellows, a compressor, a piston pump, a piston ventilator, anin-line pump, a fan, a blower, or a heat-generating device configured toprovide passive heating, such as a transformer, generator, compressor,and the like. It is also contemplated that a redundant system employingmore than one type of air moving device (e.g., both the in-line fan 550and the in-line heater 500) may be advantageous in particularly criticalapplications. Further, more than one air moving device of the same typemay be used.

The ventilator 410 shown in FIGS. 4A and 4B may be implemented as anin-line heater (e.g., the in-line heater 500 depicted in FIGS. 8A, 8B,9A, and 13A-13C) configured to heat the entire ventilation pipe 400, ora portion thereof, to induce a “chimney effect” (or stack effect) in theventilation pipe 400 that reduces the density of the gas therein andcauses it to rise. For example, the entire ventilation pipe 400, or aportion thereof, may be wrapped circumferentially with electricalheating elements (e.g., heating tape, not shown).

As is appreciated by those of ordinary skill in the art, the in-lineheater 500 is not limited to use with any particular manhole cover. InFIGS. 8A and 8B, the in-line heater 500 is illustrated being used withthe manhole cover 230D, and the in-line heater 500 is illustrated beingused with the manhole cover 230E in FIG. 9A. Further, the in-line heater500 is not limited to use with any particular implementation of theventilation pipe 400. For the sake of brevity, referring to FIG. 9A, thein-line heater 500 will be described below being used with the manholecover 230E and the implementation of the ventilation pipe 400 depictedin FIG. 9A.

FIG. 13A is a left side view of in-line heater 500. The in-line heater500 includes a heated metal pipe section 530 having the upper flange531, which may be attached to the lower flange 402 (see FIG. 8B) of thesection P1, the manifold 246A, or the lower flange 472 (see FIG. 9A) ofthe vertical section V3 (see FIGS. 4B and 9A). The pipe section 530 alsohas the lower flange 532 for attachment to the upper flange 404 (seeFIG. 8B) of the section P2 or an upper flange 474 (substantiallyidentical to the upper flange 404 illustrated in FIG. 8A) of thevertical section V4 (see FIGS. 4B and 9A) of the ventilation pipe 400.

A cutaway portion in FIG. 13A exposes the internal configuration of thein-line heater 500. As shown in FIG. 13A, electric cartridge heaters 542are inserted into thermal wells 546 that penetrate the walls of theflanged pipe section 530. The flanged pipe section 530 may beconstructed from metal to provide good heat transfer with corrosionresistivity in the damp environment. In practice, aluminum may bepreferable based on installation and cost considerations. The thermalwells 546 are sealed so as to exclude water by pipe plugs 545 andsealingly mated submersible electrical junction boxes 547. Each of theelectrical junction boxes 547 may be connected to an appropriateelectrical source (e.g., by a connection 1190 illustrated in FIGS. 21Band 31 ). For additional clarity, FIGS. 13B and 13C illustrate front andbottom views of the heater 500, respectively. In these figures, each ofthe cartridge heaters 542 has an electrical connection in acorresponding one of the electrical junction boxes 547. The multiplecartridge heaters 542 are used to create redundancy and assure long lifeof the in-line heater 500. This redundancy may also improve reliability.The in-line heater 500 may be configured to provide a desired output(e.g., greater than about 100 Watts or greater than about 400 Watts).

Power for the in-line heater 500 may be conveniently tapped from asecondary wire, a transformer, or other electrical equipment typicallypresent in the vault 12. In case that this is not available, a suitablelow voltage wire may be run from a nearby power access point to thevault 12.

The in-line heater 500 may be thermally insulated to protect personnelfrom hot metal surfaces and for the sake of energy efficiency. Further,because heating the internal atmosphere 104 (see FIG. 3 ) within thevault 12 may decrease a thermal gradient between the interiorthrough-channel 432 (see FIGS. 5A and 5B) of the ventilation pipe 400and the internal atmosphere 104 (see FIG. 3 ) within the vault 12,thermally insulating the in-line heater 500 may increase (e.g.,maximize) the flowrate within the ventilation pipe 400. It is preferredthat the in-line heater 500 is installed in a substantially verticalorientation to maximize the gas flow because, as determined by severalexperiments, the heated gases tend to stagnate in horizontal pipesections (e.g., the horizontal sections H1 and H2 shown in FIGS. 4B and9A). Any horizontal sections of the ventilation pipe 400 should beinstalled with a slight upward slope (at least about ⅛ inch or at leastabout ¼ inch of rise per foot may be used) to promote flow of thegaseous composition 106 (see FIG. 3 ) toward the manhole cover 230A andprevent accumulation of water within the ventilation pipe 400.

Furthermore, referring to FIG. 9A, the heated section of the ventilationpipe 400 is preferably installed just above the highest anticipatedwater level in the vault 12 for best ventilation (e.g., a floatingheater). For practical reasons, the in-line heater 500 is preferablyinstalled near the ceiling 56 of the vault 12 to minimize the risk ofbeing submerged in water near the floor 58 during periods of heavystreet flooding. Safety considerations also dictate that temperatures ofexposed surfaces and exhaust gases not exceed 60° C. to avoid exposingany personnel entering the vault 12 as well as pedestrians or their petsat the surface 30 to potential burn hazards. Additionally, thetemperature of any heating elements used should be kept well below theauto-ignition point (e.g., about 200° C.) of organic vapors likely to beencountered.

The in-line heater 500 may be fabricated from steel, aluminum, copper,stainless steel, brass, or bronze. Insulation is typically applied overheater 500, but again not shown in these figures. As previously noted,the ventilation pipe 400 may be formed in sections. For example, theheated metal pipe section 530 (see FIGS. 8B, 13A, and 13B) of thein-line heater 500 may be joined to a plastic pipe or corrugated plastichose (e.g., the section P2 or the vertical section V4). In such anarrangement, a thermally insulating gasket material, such as aluminumoxide, can be introduced between the plastic and metal sections toprotect the former. Other devices used to implement the ventilator 410(e.g., the in-line fan 550) may be safely used with either metal orplastic piping.

FIGS. 14A-14C illustrate an exemplary implementation of the in-line fan550 that may be used to implement the ventilator 410 (see FIGS. 4A, 4B,8A, 8B, 18, 21A, 21B, and 26 ). The in-line fan 550 is depicted infront, side, and bottom views in FIGS. 14A, 14B, and 14C, respectively.The in-line fan 550 or a similar air moving device may be inserted in asection of the ventilation pipe 400 (or between adjacent sections of theventilation pipe 400), preferably close to the ceiling 56 (see FIGS. 1,4A, 4B, 9A, 18, and 19 ) of the vault 12 (see FIGS. 1, 3-4B, 9A, 18, 19,21A, 21B, 26A, and 32 ). However, this is not a requirement. The in-linefan 550 may be oriented to blow air from the internal atmosphere 104(see FIG. 3 ) into the external atmosphere 102 (see FIG. 3 ) and viceversa.

Referring to FIGS. 14A and 14B, the in-line fan 550 has a housing 551with the upper and lower flanges 552 and 554. The upper and lowerflanges 552 and 554 are substantially identical to the upper and lowerflanges 531 and 532 (see FIGS. 8A, 8B, 9A, 13B, and 13C), respectively.Thus, the upper and lower flanges 552 and 554 may be coupled to thelower and upper flanges 402 and 404 (see FIGS. 8A and 8B), respectively.Referring to FIGS. 14B and 14C, inside the housing 551, the in-line fan550 includes rotatable fan blades 556. FIG. 14B shows the internalconfiguration of the fan blades 556.

By way of non-limiting examples, the in-line fan 550 may be implementedas either a simple axial in-line fan or an in-line centrifugal fancapable of continuous, reliable operation. As with the above describedin-line heater 500 (see FIGS. 8A, 8B, 9A, and 13A-13C), the in-line fan550 can draw power from suitable equipment within the vault 12. Thein-line fan 550 may be rated to meet the electrical classification ofthe main chamber 52 (see FIGS. 1, 4A, 4B, 9A, 18, 19, 21A, 21B, and 26 )and suitably encased to render the in-line fan 550 relativelycorrosion-resistant and dirt-resistant to provide a long service life.

Manhole Ring Support

Referring to FIG. 5A, as mentioned above, the manhole cover 230A mayrest on the ledge 254A of the manhole ring support 250A. Optionally,water ingress through a gap between the ring support 250A (see FIG. 1A)and the periphery of the manhole cover 230A may be reduced by adding atleast one partial dams 582 (see FIGS. 6A-6C) and/or partial groove ormoats 586 (see FIGS. 6A-6C) to the ring support 250A to divert flow fromthis region.

For example, referring to FIG. 6A, the ring support 250B has an upperexternal portion 580 positioned on or alongside the surface 30. Theupper external portion 580 includes two semi-circular partial ring dams582. Each of the partial dams 582 may subtend an angle from about 90degrees to about 330 degrees. Depending on local regulations, the heightof each of the partial ring dams 582 may typically be no greater thanabout ⅛ inch to about 3/16 inch above the top surface 232B of themanhole cover 230B. To properly divert water on the surface 30, thepartial ring dam 582 is positioned such that the direction from itsmidpoint to the center of the manhole cover 230B aligns with theeffective slope S1 of the surface 30 immediately adjacent to the ringdam. This direction is the resultant obtained by vectorially adding thegrade (represented by the arrow S2) of the surface 30 in a directionparallel with the road to a slope (represented by an arrow S3)perpendicular to the road.

One or more partial ring moats 586, disposed near the periphery of themanhole cover 230B, may be formed in the upper external portion 580 ofthe ring support 250B. In the embodiment illustrated, the moat 586 ispositioned between the partial ring dams 582. The moat 586 is believedto deflect water away from the manhole cover 230B and thereby furtherreduce the amount of water that can enter a gap between the ring support250B and the periphery of the manhole cover 230B. Like the ring dams582, each of the partial ring moats 586 is semi-circular, but maysubtend an angle from about 90 degrees to about 330 degrees.

The above-described partial dams 582 and ring moats 586 may have avariety of cross-sectional profiles to address tripping, noise, andtraction considerations (e.g., rectangular, beveled rectangular,chamfered rectangular, trapezoidal, filleted rectangular, or arcuate,inter alia).

The term “partial” as applied to the dams 582 and moats 586 indicatesthat these features, which are concentric with the ring support 250B,extend only partially around the ring support 250B. In other words, thepartial dams 582 and moats 586 only partially surround the manhole cover230B.

Moat(s)

One or more partial roadway moats 590, disposed near the periphery ofthe ring support 250B, may be formed in the surface 30. For example, thepartial roadway moats 590 may be cut into the surface 30. The partialroadway moats 590 and are believed to deflect water away from themanhole cover 230B and thereby further reduce the amount of water thatcan enter a gap between the ring support 250B and the periphery of themanhole cover 230B. Like the ring dams 582 and moats 586, each of thepartial roadway moats 590 is semi-circular, but may subtend an anglefrom about 90 degrees to about 330 degrees. For the purposes herein, thepartial roadway moats 590 may be arcuate, or linear, the latter versionbeing more easily cut into the existing surface 30. The partial roadwaymoats 590 may have a variety of cross-sectional profiles to addresstripping, noise, and traction considerations (e.g., rectangular, beveledrectangular, chamfered rectangular, trapezoidal, filleted rectangular,or arcuate, inter alia).

The term “partial” as applied to the roadway moats 590 indicates thatthese features, which are concentric with the ring support 250B, extendonly partially around the perimeter of the ring support 250B. In otherwords, the partial roadway moats 590 only partially surround the manholecover 230B.

One or more partial ring dams 582, partial ring moats 586, or partialroadway moats 590, or a combination of these features, may be employed(e.g., as illustrated in FIGS. 6A-6C and described above).

Optional Exhaust Hole Plug

As discussed in the Background section, a major limitation of providingadditional venting for a manhole cover is the inevitable ingress ofundesirable liquids, mainly water, and solids including snow and slush.Referring to FIG. 8A, this detraction may be addressed at least in partby the exhaust hole plug 653D. The exhaust hole plug 653D may beconfigured for insertion into any suitably shaped hole formed in amanhole cover. For the sake of brevity, the exhaust hole plug 653D isdescribed below as being configured for insertion into one of theexhaust holes 253D (see FIGS. 8E-8G) of the manhole cover 230D.

Referring to FIG. 15 , the exhaust hole plug 653D includes an exhausthole cap 654 and a support member 656. The support member 656 isattached to and extends away from a bottom surface 655 of the cap 654.The support member 656 includes multiple spacer portions or steps 658that are spaced apart from one another and positioned along theperiphery of the exhaust hole cap 654. Referring to FIG. 8C, it shouldbe noted that the section 8F-8F is taken slightly (about 1/16 inch) offcenter, so the support member 656 appears to be unsupported in thisview, but subsequent illustrations and discussion clarify thepositioning of this element.

Referring to FIG. 8G, the steps 658 (see FIG. 15 ) are configured tolimit the insertion depth of the support member 656 into the exhausthole 253D. The steps 658 (see FIG. 15 ) of the support member 656position the exhaust hole cap 654 above the top surface 232D of themanhole cover 230D. Thus, a gap 659 (see FIG. 8G) is defined between thebottom surface 655 of the exhaust hole cap 654 and the top surface 232Dof the manhole cover 230D. The gap 659 allows discharge of the dangerousgaseous composition 106 shown in FIG. 3 (through the exhaust hole 253D).A different exhaust hole plug 653D is positioned in each of the exhaustholes 253D with the exhaust hole cap 654 positioned above the topsurface 232D of the manhole cover 230D so as to leave the gap 659through which gas may flow while limiting entry of rain water anddebris.

The exhaust hole plug 653D may be press (or interference) fit into oneof the exhaust holes 253D in the manhole cover 230D. In suchembodiments, the dimensions of the support member 656 may be slightlyoversized with respect to the internal size of the exhaust holes 253D tohold the support member 656 in place by friction inside the exhaust hole253. During this pressing operation, the multiple steps 658 (best seenin FIG. 15 ) of the support member 656 limit the travel thereof into theexhaust hole 253D as the steps 658 seat or rest on the top surface 232Dof the manhole cover 230D.

The exhaust hole plug 653D is preferably fabricated from cast iron, buta material such as steel, fiberglass composite, or aluminum can be usedprovided it meets the structural requirements and does not initiategalvanic corrosion. The exhaust hole plug 653D may be cast as anintegral unit but, alternatively, may be assembled from the individualcomponents (e.g., by welding or brazing in the case of steel oraluminum). It is preferred that the exhaust hole plug 653D is amonolithic structure wherein the respective cap 654 is integral with thesupport member 656.

Optional Vent Hole Plug

Referring to FIG. 8A, like the exhaust hole plug 653D, the vent holeplug 652D is configured to at least partially limit or prevent ingressof undesirable liquids, mainly water, and solids including snow andslush into the vault 12 (see FIGS. 1, 3-4B, 9A, 18, 19, 21A, 21B, 26A,and 32 ). The vent hole plug 652D may be configured for insertion intoany suitably shaped hole formed in a manhole cover. For the sake ofbrevity, the vent hole plug 652D is described below as being used withthe manhole cover 230D and configured for insertion into one of the ventholes 252D (see FIGS. 8D, 8E, 8H and 8I).

In the embodiment illustrated in FIGS. 8H and 8I, the vent hole plug652D is substantially similar to the exhaust hole plug 653D (see FIGS.8A-8C, 8F, 8G, 9A, 15, and 19 ) but is configured for insertion into oneof the vent holes 252D, instead of one of the exhaust holes 253D (seeFIGS. 8E-8G). Referring to FIG. 16 , the vent hole plug 652D includes avent hole cap 664 and a support member 666. The support member 666 isattached to and extends away from a bottom surface 665 of the cap 664.The support member 666 may have multiple spacer portions or steps 668that are spaced apart from one another and positioned along theperiphery of the vent hole cap 664. As mentioned above, referring toFIG. 8C, the section 8F-8F is taken slightly (about 1/16 inch) offcenter, so in FIG. 8I the support member 666 appears to be unsupported,but subsequent illustrations and discussion clarify the positioning ofthis element.

Referring to FIG. 8I, the steps 658 (see FIG. 16 ) are configured tolimit the depth to which the support member 666 can be inserted into thevent hole 252D. The steps 668 (see FIG. 16 ) of the support member 666position the vent hole cap 664 above the top surface 232D of the manholecover 230D. Thus, a gap 669 is defined between the bottom surface 665 ofthe exhaust hole cap 654 and the top surface 232D of the manhole cover230D. The gap 669 allows make-up air to enter the vault 12 (through thevent hole 252D). A different vent hole plug 652D is positioned in eachof the vent holes 252D with the vent hole cap 664 positioned above thetop surface 232D of the manhole cover 230D so as to leave the gap 669through which air may flow into the vault 12 while limiting entry ofrain water and debris.

The vent hole plug 652D may be press (or interference) fit into one ofthe vent holes 252D in the manhole cover 230D. In such embodiments, thedimensions of the support member 666 may be slightly oversized withrespect to the internal size of the vent holes 252D to hold the supportmember 666 in place by friction inside the vent hole 252. During thispressing operation, the multiple steps 668 (best seen in FIG. 16 ) ofthe support member 666 limit the travel thereof into the vent hole 252Das the steps 668 seat or rest on the top surface 232D of the manholecover 230D.

The vent hole plug 652D is preferably fabricated from cast iron, but amaterial such as steel, fiberglass composite, or aluminum can be usedprovided it meets the structural requirements and does not initiategalvanic corrosion. The vent hole plug 652D may be cast as an integralunit but, alternatively, may be assembled from the individual components(e.g., by welding or brazing in the case of steel or aluminum). It ispreferred that vent hole plug 652D is a monolithic structure wherein thecap 664 is integral with the support member 666.

Alternate Embodiment of Vent Hole Plug

FIG. 10A illustrates the vent hole plug 652F for use with the manholecover 230F. The vent hole plug 652F is configured to be inserted intoone of the vent holes 252F. The vent hole plug 652F may be constructedfrom any materials suitable for constructing the vent hole plugs 652D(see FIGS. 8A-8D, 8H, 8I, and 16 ).

Referring to FIGS. 17A-17C, the vent hole plugs 652F each includes around vent hole cap 674 and a support member 676. Referring to FIG. 17B,the support member 676 is attached to and extends away from a bottomsurface 675 (see FIG. 17B) of the cap 674. It is preferred that venthole plug 652F is a monolithic structure wherein the cap 674 is integralwith the support member 676. Like the support member 666 (see FIGS. 8Iand 16 ) of the vent hole plug 652D (see FIGS. 8A-8D, 8H, 8I, and 16 ),the support member 676 includes multiple spacer portions or steps 678that are spaced apart from one another and positioned along theperiphery of the vent hole cap 674.

Referring to FIG. 10F, the steps 678 (see FIGS. 17B and 17C) areconfigured to limit the insertion depth of the support member 676 intothe vent hole 252F. The steps 678 (see FIGS. 17B and 17C) of the supportmember 676 position the vent hole cap 664 above the annular ledge 296.Thus, a gap 679 is defined between the bottom surface 675 of the exhausthole cap 654 and the annular ledge 296. The gap 679 allows discharge ofthe dangerous gaseous composition 106 shown in FIG. 3 (through the venthole 252F). Referring to FIG. 10F, a different vent hole plug 652F ispositioned in each of the vent holes 252F with the vent hole cap 664positioned above the annular ledge 296 so as to leave the gap 679through which gas may flow while limiting entry of rain water anddebris.

The exhaust hole plug 653D (see FIGS. 8A-8C, 8F, 8G, 9A, 15 , and 19),the vent hole plug 652D (see FIGS. 8A-8D, 8H, 8I, and 16 ), and/or thevent hole plug 652F (see FIGS. 10A, 10B, 10D-10F, and 17A-17C) may beadapted or retrofitted for use with existing manhole covers (e.g., themanhole cover 70 depicted in FIG. 2 ) having vent holes (e.g., the ventholes 72 depicted in FIG. 2 ). In such a manhole cover, some preexistingholes may be selected for exhaust and others for vents. Optionally, anappropriate manifold (e.g., one of the manifolds 246A, 246D, and 460illustrated in FIGS. 7, 8A, and 11A, respectively) may be used.

Second Embodiment of Ventilation System

FIG. 18 depicts a second embodiment of a ventilation system 710installed in the vault 12. Like the ventilation system 210 (see FIGS.4A-5B, 6A, 7-8C, 9A, and 9B), the ventilation system 710 is an exemplaryimplementation of the ventilation system 100 (see FIG. 3 ). As mentionedabove, referring to FIG. 3 , instead of effecting the air exchange(represented by the arrows A1 and A2), across the interface 92 formed bythe manhole cover 130, at least part of the air exchange (represented bythe arrows A1′ and A2′) may occur within alternative channels or ducts(e.g., the ventilation stack 132) connected to the main chamber 52. Forexample, referring to FIG. 18 , the ventilation pipe 400 may be fluidlyconnected directly to the vent stack 132. In such embodiments, the airmoving assembly 240 may move internal air into the vent stack 132, whichexits therefrom (represented by the arrow A2′ in FIG. 3 ) into theexternal atmosphere 102 (see FIG. 3 ). In such embodiments, external airmay enter the vault 12 through other means, such as through one or morevent holes 752 formed in a manhole cover 730 (represented by the arrowA1 in FIG. 3 ).

FIG. 18 depicts the vent stack 132 displaced from the manhole cover 730by (typically) more than one foot to about three feet. In this case, thefirst open end 440 of ventilation pipe 400 is sealably connected to thevent stack 132 at a point where the latter penetrates one of thesidewall(s) 54 of the main chamber 52 of the vault 12. Since the ductdiameter associated with the vent stack 132 is typically larger thanthat of the ventilation pipe 400, a transition connector or annular plug732 may be used to couple these two features together using methods wellknown in the art. The ventilation pipe 400 extends into the main chamber52 of the vault 12 and may position at least one second opening 448proximal to the second open end 442 of the ventilation pipe 400 at avertical level of less than or equal to about 3 feet above the floor 58of the main chamber 52.

As discussed above, the ventilation pipe 400 may include the one or moresecond openings 448. For example, the ventilation pipe 400 may include aplurality of second openings 448 (e.g., the holes 449 depicted in FIG.9A) formed in the wall(s) 430 (see FIGS. 5A, 5B, 19, and 20 ). Thesecond openings 448 may be configured to allow ventilation to occur evenas water level rises in the vault 12. The second openings 448 may have auniform size and shape or be graduated (or variegated) to draw air from(or push air through) larger holes located lower in the vault 12.Further, one or more of the second openings 448 may be a slit or includea flap portion (like the flap portion 447 illustrated in FIG. 20 )configured to remain closed until the water level rises.

The ventilation pipe 400 may be positioned away from the sidewall(s) 54as shown in FIG. 18 . An alternative configuration and positioning ofthe ventilation pipe 400 is shown using dashed lines. In the alternativeconfiguration, the ventilation pipe 400 hugs at least one of thesidewall(s) 54 of the main chamber 52 and may optionally be fastenedthereto.

As mentioned above, the manhole cover 730 may include at least one venthole 752 (similar to the vent hole 252A shown in FIGS. 5A and 5B or thevent holes 72 shown in FIG. 2 ) configured to allow make-up air to enterthe vault 12. Alternatively, make-up air may be drawn from the conduits20A-20C (see FIGS. 1 and 32 ), as well as from unavoidable air leaksinto the vault 12. Optionally, when the intent is to draw contaminatedgases from the conduits 20A-20C (see FIG. 1 ) entering and/or leavingthe vault 12, the vent hole(s) 752 in the manhole cover 730 may beappropriately plugged.

Optionally, a second vent stack (not shown) substantially identical tothe vent stack 132 may be connected to the main chamber 52 andconfigured to provide make-up air to the vault 12. In this case, thesecond vent stack (not shown) may be displaced from the (first) ventstack 132. Additionally, the manhole cover 730 no longer requires thevent hole(s) 752. The second vent stack (not shown) may be installedduring initial construction of the vault 12 or added at a later time.

The ventilation system 710 may be readily converted to the ventilationsystem 210 (described above and illustrated in FIGS. 4A-5B, 6A, 7-8C,9A, and 9B) by fluidly connecting the first open end 440 of theventilation pipe 400 to one or more exhaust holes or vent holes formedin the manhole cover 730 (or a different manhole cover) optionally usinga manifold (e.g., the manifold 246A depicted in FIGS. 7, 9B, and 19 ,the manifold 246D depicted in FIGS. 8A, 8B, 8D, 8F, and 8H, or themanifold 460 depicted in FIGS. 11A-11C). For example, referring to FIG.9B, the first open end 440 of the ventilation pipe 400 may be connectedto the port 330A of the manifold 246A which is connected the exhaustholes 253E of the manhole cover 230E (see FIGS. 9A and 9B,respectively).

Third Embodiment of Ventilation System

FIG. 19 depicts a third embodiment of a ventilation system 810 installedin the vault 12. Like the ventilation system 210 (see FIGS. 4A-5B, 6A,7-8C, 9A, and 9B), the ventilation system 810 is an exemplaryimplementation of the ventilation system 100 (see FIG. 3 ). However, theventilation system 810 omits the ventilator 410 (see FIGS. 4A, 4B, 8A,8B, 18, 21A, 21B, and 26 ). Instead, the ventilation pipe 400 acts aloneas a passive ventilator using the chimney (stack) effect (describedabove). Therefore, the ventilator 410 is not required.

In FIG. 19 , the ventilation pipe 400 extends into the vault 12 suchthat at least one of the second openings 448 is located at most aboutthree feet above the floor 58. In the embodiment illustrated, theventilation pipe 400 includes a plurality of the second openings 448(e.g., the holes 449 depicted in FIG. 9A) formed in the wall(s) 430. Thesecond openings 448 may be configured to allow ventilation to occur evenas water level rises in the vault 12. The second openings 448 may have auniform size and shape or be graduated (or variegated) to draw air from(or push air through) larger holes located lower in the vault 12.Further, one or more of the second openings 448 may be a slit or includea flap portion (like the flap portion 447 illustrated in FIG. 20 )configured to remain closed until the water level rises.

As mentioned above, the vault 12 may partially flood from time to timedue to heavy precipitation. In FIG. 19 , the vault 12 is illustratedpartially filled with the water 80. The highest water level 812 abovethe floor 58 is designated herein as an “effective floor” because theventilation pipe 400 cannot draw any of the internal atmosphere 104(e.g., the gaseous composition 106 depicted in FIG. 3 ) from a locationbelow this vertical level.

A line 814 illustrates an ignition level that is (e.g., about 6 inches)above a lowest non-submerged source of ignition 816. It should be clearthat a submerged ignition source would not initiate a fire or explosion.By way of non-limiting examples, one or more of the following sources ofignition may be present in the vault 12:

-   -   1. an exposed conductor on a live-front termination of        underground equipment (e.g., transformer and/or switchgear)        located in the vault 12;    -   2. a termination of dead-front underground equipment;    -   3. secondary cables;    -   4. joints; and    -   5. T-bodies that connect together two pieces of medium voltage        or low voltage secondary cables that are usually mounted on the        sidewall(s) 54 of the vault 12 above the floor 58.

The effective floor concept may be used to determine how far theventilation pipe 400 should extend into the vault 12 such that thevertical height of at least one of the second openings 448 is betweenthe line 814 representing the ignition level and the effective floor812. Although the level of the effective floor 812 is somewhatpredictable from past experience in the immediate vicinity of the vault12, the level of the effective floor 812 cannot be precisely known orguaranteed. However, the float assembly 412 shown in FIG. 12 follows thelevel of the water 80 and therefore, the level of the effective floor812. The float assembly 412 allows only air that flows between thefloats 690 to enter the bellows 682 (and the second openings 448positioned inside the bellows 682). Thus, the level of the openings 692between the floats 690 is an effective intake level that is determinedby the level of the water 80 (see FIGS. 3 and 19 ). In this manner, thefloat assembly 412 may be used to automatically adjust the height of theeffective intake level so as to maintain it above the effective floor812.

This approach to determining the effective intake level may be appliedto any other embodiment described, regardless of whether the exhaust isactive (e.g., the ventilator 410 is used) or passive (e.g., only theventilation pipe 400 is used).

Fourth Embodiment of Ventilation System

FIG. 21A illustrates a fourth embodiment of a ventilation system 910.Like the ventilation system 210 (see FIGS. 4A-5B, 6A, 7-8C, 9A, and 9B),the ventilation system 910 is an exemplary implementation of theventilation system 100 (see FIG. 3 ). The ventilation system 910 may beconfigured to move (or draw) at least a portion of the externalatmosphere 102 (see FIG. 3 ) into the main chamber 52, which causes aportion of the internal atmosphere 104 (see FIG. 3 ) to exit (orexhaust) from the main chamber 52. Alternatively or additionally, theventilation system 910 may be configured to push (or blow) at least aportion of the internal atmosphere 104 (see FIG. 3 ) from the mainchamber 52 into the external atmosphere 102 (see FIG. 3 ). In thisembodiment, the interface 92 (see FIG. 3 ) is implemented as a manholecover 230G and the air moving assembly 90 (see FIG. 3 ) is implementedas an air moving assembly 914. The ventilation system 910 may includethe ventilation stack 132 (see FIG. 3 ). However, this is not arequirement and the ventilation stack 132 (see FIG. 3 ) has been omittedfrom FIG. 21A.

Optionally, referring to FIG. 21A, the ventilation system 910 mayinclude the ring support 250G. In the implementation illustrated, themanhole cover 230G is supported by the ring support 250G configured toprovide the same functionality as the ring supports 250A and 250Billustrated in FIGS. 5A and 6A, respectively. Referring to FIG. 21A, thering support 250G may include a ledge 254G (see FIG. 26A) that issubstantially identical to the ledge 254A (see FIGS. 5A, 5B, and 9B) andupon which the manhole cover 230G rests. Referring to FIG. 26A, the ringsupport 250G also has an inside surface 256G positioned below the ledge254G that faces into the neck 60. The ring support 250G may beconfigured to include at least one dam 582 (see FIGS. 6A-6C) and/or atleast one moat 586 (see FIGS. 6A-6C). Further, at least one moat 590(see FIGS. 6A-6C) may be formed in the surface 30 alongside the manholecover 230G. Optionally, a waterproof seal (like the seal 251 illustratedin FIG. 5C) may be positioned between the manhole cover 230G and thering support 250G. The seal (not shown) is configured to help preventwater intrusion between the manhole cover 230G and the ring support250G. The seal (not shown) may be implemented as a gasket, an O-ring,putty, caulk, a combination thereof, and the like.

Manhole Cover

Referring to FIGS. 22A and 22B, the manhole cover 230G has an outwardlyfacing top side 918 opposite an inwardly facing bottom side 919.Referring to FIG. 22A, the manhole cover 230G has a center portion 920surrounded by a peripheral edge 921. Although the manhole cover 230G hasbeen illustrated as having a traditional round manhole cover shape, themanhole cover 230G may have an alternate shape, such as rectangular.

A plurality of outlets or exhaust holes 253G are positioned adjacent tothe center portion 920 and a plurality of inlets or vent holes 252G arepositioned adjacent to the peripheral edge 921. In the embodimentillustrated, the vent and exhaust holes 252G and 253G do not overlapradially. However, this is not a requirement. The vent holes 252G (whichare implementations of the vent holes 152 depicted in FIG. 3 ) allow aportion (represented by the arrow A1 in FIG. 3 ) of the externalatmosphere 102 (see FIG. 3 ) to flow into the internal atmosphere 104(see FIG. 3 ). On the other hand, the exhaust holes 253G (which areimplementations of the exhaust holes 153 depicted in FIG. 3 ) allow aportion (represented by the arrow A2 in FIG. 3 ) of the internalatmosphere 104 (see FIG. 3 ) to flow into the external atmosphere 102(see FIG. 3 ). However, as explained above, the exhaust holes 253G maybe converted to vent holes and the vent holes 252G may be converted toexhaust holes by reversing the direction of the flow therethrough.

Referring to FIGS. 22A and 22B, it may be beneficial to maximize theoverall size (area) of the vent and exhaust holes 252G and 253G toreduce flow restrictions posed by the manhole cover 230G. However, as isapparent to those of ordinary skill in the art, the vent and exhaustholes 252G and 253G should be configured such that structural integrityof the manhole cover 230G is adequate to withstand normal usage (e.g.,usage specified by OSHA 1926.502, AASHTO-M306, etc.).

Like other manhole covers discussed above (e.g., the manhole covers 230Dand 230F shown in FIGS. 8A and 10A, respectively), the manhole cover230G may include water control features. For example, referring to FIG.22A, the top side 918 may include channels 924 arranged to providethroughways through which precipitation and surface water may flow. Thechannels 924 direct surface water away from the vent and exhaust holes252G and 253G. The channels 924 may define a top surface portion 922 inwhich information (e.g., branding, logos, etc.) may be displayed.

In the embodiment illustrated, the channels 924 are spaced apart fromeach of the vent and exhaust holes 252G and 253G and define a dam-likeportion 926 that partially or completely surrounds each of the vent andexhaust holes 252G and 253G. These dam-like portions 926 help preventsurface water from entering the vent and exhaust holes 252G and 253G.Because the top side 918 includes the channels 924 instead of elevationwalls (like the elevation wall(s) 235D illustrated in FIGS. 8C and 8E orthe elevation walls 298 illustrated in FIGS. 10B, 10C, and 10E), lessnoise may be produced by vehicles driving over the manhole cover 230G.

Optionally, a plurality of the vent hole plugs 652D (see FIGS. 8A-8D,8H, 8I, and 16 ) may be inserted one each into some of the vent holes252G and/or a plurality of the vent hole plugs 652F (see FIGS. 10A, 10B,10D-10F, and 17A-17C) may be inserted one each into some of the ventholes 252G. Similarly, a plurality of the exhaust hole plugs 653D (seeFIGS. 8A-8C, 8F, 8G, 9A, 15, and 19 ) may be inserted one each into theexhaust holes 253G.

The top side 918 of the manhole cover 230G may have a curved orgenerally domed shape that is taller near the center portion 920 andcurves downwardly toward the peripheral edge 921. This domed shape helpsdirect water away from the center portion 920 and toward the peripheraledge 921. The domed shape also positions the vent and exhaust holes 252Gand 253G above the surface 30 (see FIGS. 1, 3-6C, 9A, 9B, 18, 19, 21A,26A, and 32 ) by a predetermined amount (e.g., about ⅛ inch, about ⅜inches in accordance with requirements specified by Americans withDisabilities Act, at least about ⅛ inches, or about ⅜ inches.

Along its periphery, the manhole cover 230G includes one or moreconventional closed end wells 928 configured to be used to lift themanhole cover 230G from the manhole 62. Each of the wells 928 extendsradially inward from the peripheral edge 921 toward the center portion920 and passes under a transverse bridge portion 929. The worker 61 (seeFIGS. 1 and 3 ) may insert a tool (e.g., a pick, not shown) into one ofthe wells 928, hook onto the bridge portion 929, and lift the manholecover 230G upwardly and out of the manhole 62.

Optionally, referring to FIG. 22B, the bottom side 919 includes adownwardly extending ring-shaped wall 940 that surrounds the exhaustholes 253G. Implementations that include the ring-shaped wall 940 mayomit one of the manifolds 246A (see FIGS. 7, 9B, and 19 ), 246D (seeFIGS. 8A, 8B, 8D, 8F, and 8H), and 460 (see FIGS. 11A-11C). The bottomside 919 may include a downwardly extending structure 944 positionedinside the wall 940. In the embodiment illustrated, the structure 944 isgenerally hexagonally shaped and positioned at or near the centralportion 920 of the manhole cover 230G. A plurality of support walls 948extend radially outwardly from the structure 944 and pass throughrounded fillets 949 formed in the wall 940. Each of the walls 948 has atapered distal end portion 952 that terminates before reaching theperipheral edge 921. The exhaust holes 253G are positioned between thestructure 944 and the wall 940. The vent holes 252G are positionedbetween the wall 940 and the peripheral edge 921.

The manhole cover 230G may be used instead and in place of the manholecovers 230A-230F in the first three embodiments described above. In suchimplementations, the vent holes 252G may optionally be used as exhaustholes and the exhaust holes 253G may optionally be used as vent holes.However, this is not a requirement.

While the ventilation system 910 has been described as including themanhole cover 230G, the ventilation system 910 may alternatively includeone of the manhole covers 230A-230F illustrated in FIGS. 5A, 6A, 7, 8A,9B, and 10A, respectively. Furthermore, the manhole cover 230G may beimplemented by retrofitting a conventional manhole cover (e.g., thevented manhole cover 70 illustrated in FIG. 2 ) by creating the ventholes 252G and/or the exhaust holes 253G in an otherwise solid cover,plugging some existing holes (e.g., the vent holes 72 illustrated inFIG. 2 ), and/or adding the ring-shaped wall 940 to the underside of themanhole cover.

Air Moving Assembly

Referring to FIG. 21B, the air moving assembly 914 includes theventilation pipe 400 and the ventilator 410. Optionally, the air movingassembly 914 may include the optional float assembly 412 (see FIG. 12 ).The air moving assembly 914 may include a support bracket assembly 960and/or one of the optional manifolds 246A (see FIGS. 7, 9B, and 19 ),246D (see FIGS. 8A, 8B, 8D, 8F, and 8H), and 460 (see FIGS. 11A-11C).However, as mentioned above, when the manhole cover 230G is used, amanifold is not necessary. As will be described in further detail below,the ventilator 410 may be implemented as a ventilator assembly 1100 (seeFIGS. 27 and 30-32 ).

Support Bracket Assembly

Referring to FIG. 23 , the support bracket assembly 960 has a pluralityof mounting assemblies 961-964 coupled to a support frame 965. Referringto FIG. 24 , the support frame 965 includes a ring-shaped wall 966having an upper edge portion 967 configured to couple to the ring-shapedwall 940 (see FIGS. 21B and 22B) of the manhole cover 230G (see FIGS.21A-22B, 31 , and 32). Optionally, a seal (not shown) may be positionedbetween the walls 940 and 966. The ring-shaped wall 966 includes slotsor cutouts 971-974 that extend downwardly from the upper edge portion967.

The support frame 965 includes a plurality of elongated frame members981-984 that extend outwardly from a center portion 985. The framemembers 981-984 are substantially identical to one another. The framemembers 981-984 extend from the center portion 985, through the cutouts971-974, respectively, and are affixed to the ring-shaped wall 966within the cutouts 971-974, respectively. The frame members 981 and 983are aligned with one another longitudinally and are therefore collinearwith one another. Similarly, the frame members 982 and 984 are alignedwith one another longitudinally and are therefore collinear with oneanother. In the embodiment illustrated, inside angles of approximately90 degrees are defined between adjacent ones of the frame members981-984. However, this is not a requirement. Each of the frame members981-984 has a free distal end 986 with an opening 987 into alongitudinally extending channel 988. Further, each of the frame members981-984 has one or more transverse through-holes 989 that providelateral access into the channel 988 of the frame member. Referring toFIG. 23 , the through-holes 989 (see FIG. 24 ) are each configured toreceive a fastener F4 (e.g., a set screw). In the embodimentillustrated, an outwardly extending threaded portion 980 surrounds eachof the through-holes 989 (see FIG. 24 ). The threaded portions 980 eachhave inside threads aligned with the through-hole 989 (see FIG. 24 ) andconfigured to mate with outside threads formed on each of the fastenersF4. Thus, the fasteners F4 maybe threaded into and out of thethrough-holes 989 (see FIG. 24 ).

Referring to FIG. 23 , the mounting assemblies 961-964 are substantiallyidentical to one another. For the sake of brevity, only the mountingassembly 961 will be described in detail below. However, the likereference numerals have been used to identify substantially identicalcomponents of the mounting assemblies 961-964.

Referring to FIG. 25 , the mounting assembly 961 has an elongatedsupport member 990 configured to be received inside the channel 988 (seeFIG. 24 ) of the frame member 981 (see FIG. 24 ) and to slidelongitudinally (horizontally) therein. Thus, the support members 990 ofthe mounting assemblies 961-964 (see FIG. 23 ) may be characterized astelescoping (horizontally) with respect to the frame members 981-984(see FIG. 23 ), respectively. Referring to FIG. 23 , the fasteners F4may be threaded into the through-holes 989 (see FIG. 24 ) and positionedtherein to laterally engage the support members 990 and prevent thesupport members 990 from sliding within the channels 988 (see FIG. 24 ).In this manner, referring to FIG. 23 , the fasteners F4 lock the(horizontal) position of the support members 990 of the mountingassemblies 961-964 with respect to the frame members 981-984,respectively.

Referring to FIG. 25 , the support member 990 has a distal end 992configured to be positioned outside the channel 988 (see FIG. 24 )beyond the free distal end 986 (see FIG. 24 ) of the frame member 981.An upright support member 994 is coupled to the distal end 992 of thesupport member 990. The upright support member 994 has one or moresidewalls 995 that define a through-channel 996. At least one transversethrough-hole 998 is formed in one of the sidewalls 995 and configured toprovide lateral access into the through-channel 996. The through-hole998 is configured to receive a fastener F5 (e.g., a set screw). In theembodiment illustrated, an outwardly extending threaded portion 999surrounds the through-hole 998. The threaded portion 999 has insidethreads aligned with the through-hole 998 and configured to mate withoutside threads formed on the fastener F5. Thus, the fastener F5 may bethreaded into and out of the through-hole 998.

The through-channel 996 is configured to receive an upright slidingmember 1000 that is configured to slide within the through-channel 996of the upright support member 994. Thus, the sliding member 1000 may becharacterized as telescoping (vertically) with respect to the uprightsupport member 994. The fastener F5 may be inserted into thethrough-hole 998 and positioned therein to laterally engage the slidingmember 1000 and prevent the sliding member 1000 from sliding within thethrough-channel 996. In this manner, the fastener F5 may be used to lockthe (vertical) position of the sliding member 1000 with respect to theupright support member 994.

The sliding member 1000 has an upper end portion 1002 with transversetube-shaped member 1006 coupled thereto. The tube-shaped member 1006 hasa through-channel 1008 formed therein configured to slideably receive apin 1010. In the embodiment illustrated, the tube-shaped member 1006traverses a through-hole 1012 formed in the upper end portion 1002 andis welded to the sliding member 1000. The tube-shaped member 1006 has anend face 1007 that faces away from the sliding member 1000. Thetube-shaped member 1006 has a transverse through-hole 1020 that passesthrough the through-channel 1008 between the sliding member 1000 and theend face 1007. The through-hole 1020 provides lateral access into thethrough-channel 1008 and is configured to receive a fastener F6 (e.g., acotter pin).

The pin 1010 has a body portion 1028 configured to slide within thethrough-channel 1008 and a head portion 1030 that is too large to enterand pass through the through-channel 1008. A series of spaced apartthrough-holes 1034 are formed in the body portion 1028. The pin 1010 maybe characterized as telescoping (horizontally) with respect to thetube-shaped member 1006 and the sliding member 1000. As the body portion1028 of the pin 1010 slides within the through-channel 1008 of thetube-shaped member 1006, a different one of the through-holes 1034 maybe selectively aligned with the transverse through-hole 1020. Then, thefastener F6 may be inserted through the transverse through-hole 1020 andinto the selected through-hole 1034 formed in the pin 1010. In thismanner, the fastener F6 may be used to lock the position of the pin 1010with respect to the tube-shaped member 1006 and the sliding member 1000.The body portion 1028 of the pin 1010 has a free distal end 1038configured to be inserted into a hole 1040 (see FIG. 26B) drilled tosufficient depth (e.g., ¾ inch) in the inside surface 256G (see FIGS.26A and 26B) of the ring support 250G (see FIGS. 21A, 21B, and 26 ).

Referring to FIG. 26B, the support bracket assembly 960 is coupled tothe ring support 250G by positioning the free distal ends 1038 (see FIG.25 ) of the pins 1010 of the mounting assemblies 961-964 within theholes 1040 drilled in the inside surface 256G of the ring support 250G.Referring to FIG. 25 , the fasteners F4-F6 may be loosened and/orremoved and the positions of the support members 990, the slidingmembers 1000, and the pins 1010, respectively, adjusted so that the freedistal ends 1038 of the pins 1010 mate with the holes 1040 (see FIG.26B) drilled in the inside surface 256G of the ring support 250G. Inthis manner, the pins 1010 maintain the ring-shaped wall 966 centeredwithin a diameter of the ledge 254G and locate the support bracketassembly 960 at a given height within the ring support 250G. Byadjusting the positioning of the support members 990, the slidingmembers 1000, and the pins 1010 with respect to the support frame 965(see FIGS. 23, 24, and 26 ), the support bracket assembly 960 may beconfigured for use with ring supports (like the ring support 250G)having different inside shapes and sizes as well as to conform to theholes 1040 (see FIG. 26B) that may be hand drilled and not be preciselylocated. This adjustability also allows the ring-shaped wall 966 to becentered, leveled, and/or height adjusted so that when the manhole cover230G is installed, the upper edge portion 967 of the ring-shaped wall966 is in contact or in near proximity with the ring-shaped wall 940.

The support bracket assembly 960 may be easy to install, operate, andremove. On initial installation, the telescoping features are utilizedby an installation craftsmen (e.g., the worker 61 illustrated in FIGS. 1and 3 ) to correctly position the ring-shaped wall 996 for mating withthe ring-shaped wall 940. For example, the worker 61 (see FIGS. 1 and 3) may grasp one of the frame members 981-984, insert the support bracketassembly 960 into the ring support 250G via the manhole 62. Then, theworker 61 (see FIGS. 1 and 3 ) may adjust the support member 990 and thesliding members 1000 to place the end face 1007 of the tube-shapedmembers 1006 in contact with the inside surface 256G at each of the fourholes 1040 (see FIG. 26B) drill therein. Then, the fasteners F4 and F5(e.g., set screws) are tightened. The pins 1010 are slid into the holes1040 (see FIG. 26B) as far as they will go and affixed with thefasteners F6 (e.g., cotter pins). To remove the support bracket assembly960, all the fasteners F4 and F5 (e.g., set screws) may be left fullytightened such that the support bracket assembly 960 remains essentiallyrigid and fixed in configuration. Then, the fasteners F6 (e.g., cotterpins) and the pins 1010 may be removed freeing the support bracketassembly 960.

It may be beneficial to identity the rotational positional of thesupport bracket assembly 960 within the ring support 250G (e.g., byspray painting one of the frame members 981-984 and its immediatesurroundings) before removing the support bracket assembly 960. Thisallows the support bracket assembly 960 to be installed withoutperforming system alignment.

The support bracket assembly 960 may be configured to be durable. By wayof non-limiting examples, the support bracket assembly 960 may beconstructed from aluminum alloys, plated steel, stainless steel,fiberglass, etc.

Ventilation Pipe

As mentioned above, referring to FIG. 21B, the air moving assembly 914includes the ventilation pipe 400. In the implementation illustrated,the ventilation pipe 400 includes the sections P1 and P2. However,alternate arrangements, such as those described above, may be used. Inthe implementation illustrated, the ventilator 410 is positioned betweenthe sections P1 and P2. The section P1 may have a tapered shape and maybe constructed from a rigid material (e.g., metal, fiberglass, PVC, andthe like).

The section P2 may have a generally cylindrical shape. In theimplementation illustrated, the section P2 is flexible and optionallyconfigured to collapse (or function like a bellows) to be compacted (orcollapsed) during installation, transport, and/or removal. For example,referring to FIG. 21A, the portion P2 may be collapsed to a relativelyshort length by hooking onto the second open end 442 (e.g., using a hookattached to a line or pole) and lifting the second open end 442upwardly. The section P2 may be constructed from a durable fabric (e.g.,neoprene coated polyester) that is chemically resistant, UV resistant,steam resistant, non-conductive, and/or water proof. The section P2 maybe durable enough to withstand being dragged across the surface 30 anddropped thereupon.

In this embodiment, referring to FIG. 26A, the first open end 440 (whichis positioned on an upper end of the section P1) is coupled to thesupport bracket assembly 960 (that is attached to the ring support250G). In the embodiment illustrated, the first open end 440 is clamped(e.g., by a band or pipe clamp 1050) to the support bracket assembly960.

In this embodiment, the section P1 omits the lower flange 402 (see FIGS.8A and 8B). Similarly, the section P2 omits the upper flange 404 (seeFIGS. 8A and 8B). Instead, the lower end 401 of the section P1 and theupper end 403 of the section P2 are both coupled to the ventilator 410.Referring to FIG. 21B, in the embodiment illustrated, the lower end 401of the section P1 may be clamped (e.g., by a band or pipe clamp 1052) tothe ventilator 410 and the upper end 403 of the section P2 may beclamped (e.g., by a band or pipe clamp 1054) to the ventilator 410.

Referring to FIG. 21A, the second open end 442 may be positioned near(e.g., at a predetermined distance from) the floor 58. In this manner,the ventilator 410 may expel air into and/or remove air from the vault12 near the floor 58, which will circulate a portion of the internalatmosphere 104 (see FIG. 3 ) near the floor 58.

As discussed above, the ventilation pipe 400 may include the one or moresecond openings 448. For example, the section P2 may include a pluralityof second openings 448 (e.g., the holes 449 depicted in FIG. 9A) formedin the wall(s) 430 (see FIGS. 5A, 5B, 19, and 20 ). The second openings448 may be configured to allow ventilation to occur even as water levelrises in the vault 12. The second openings 448 may have a uniform sizeand shape or be graduated (or variegated) to draw air from (or push airthrough) larger holes located lower in the vault 12. Further, one ormore of the second openings 448 may be a slit or include a flap portion(like the flap portion 447 illustrated in FIG. 20 ) configured to remainclosed until the water level rises.

Optionally, the ventilation pipe 400 may include the float assembly 412(see FIG. 12 ). For example, the flange 680 (see FIG. 12 ) of theoptional float assembly 412 (see FIG. 12 ) may be attached to or nearthe upper end 403 of the section P2 and the bellows 682 (see FIG. 12 )may extend downwardly along the section P2. The second open end 442 maybe positioned on the support block 686 (see FIG. 12 ). In suchembodiments, one or more second openings 448 may be formed in thewall(s) 430 (see FIGS. 5A, 5B, 19, and 20 ) of the section P2 within thebellows 682. Referring to FIG. 20 , each of the one or more secondopenings 448 may include the flap portion 447.

Alternatively, referring to FIG. 21A, the float subassembly 684 (seeFIG. 12 ) without the other components of the float assembly 412 (seeFIG. 12 ) may be coupled to the second open end 442. In suchembodiments, the second open end 442 is not positioned on the supportblock 686 (see FIG. 12 ). Instead, the float subassembly 684 (see FIG.12 ) raises and lowers the second open end 442 as the level of the floodwater changes within the vault 12. In this manner, the float subassembly684 maintains at least one second opening 448 above the water and influid communication with the internal atmosphere 104 (see FIG. 3 )inside the vault 12. Referring to FIG. 20 , each of the one or moresecond openings 448 may include the flap portion 447.

Referring to FIG. 30 , the through-channel 432 of the ventilation pipe400 is large enough to move a desired amount of air. As in otherembodiments, referring to FIG. 21A, the ventilation pipe 400 may beconfigured to deliver air to and/or remove air from any location withinthe vault 12. For example, multiple second openings 448 may be formed inthe ventilation pipe 400 at desired locations.

Ventilator Assembly

Referring to FIG. 21A, as mentioned above, in the ventilation system910, the ventilator 410 may be implemented as the ventilator assembly1100 illustrated in FIG. 27 . Referring to FIG. 27 , the ventilatorassembly 1100 may be oriented to blow air from the external atmosphere102 (see FIG. 3 ) into the internal atmosphere 104 (see FIG. 3 ) or viceversa.

As shown in FIG. 27 , the ventilator assembly 1100 has an outer housing1110 formed by a substantially hollow outer housing body 1112 and ahousing cover 1114. The outer housing body 1112 has an open first end1120 opposite an open second end 1122. Referring to FIG. 30 , the openfirst and second ends 1120 and 1122 (see FIGS. 27 and 30 ) are eachconnected to the ventilation pipe 400 and in fluid communication withthe interior through-channel 432 of the ventilation pipe 400. The openfirst end 1120 may be inserted inside the lower end 401 of the sectionP1 and coupled thereto by the pipe clamp 1052. Similarly, the opensecond end 1122 may be inserted inside the upper end 403 of the sectionP2 and coupled thereto by the pipe clamp 1054. In the embodimentillustrated, the outer housing body 1112 has a generally cylindricalouter shape with a generally circular cross-sectional shape.

Referring to FIG. 27 , in the embodiment illustrated, the housing cover1114 is generally planar and ring shaped. The housing cover 1114 iscoupled to and partially closes the open first end 1120 of the outerhousing body 1112. An airtight seal may be formed along a peripheraledge 1126 of the housing cover 1114 between the housing cover 1114 andthe open first end 1120 of the outer housing body 1112. The housingcover 1114 has a central opening 1128.

An inner housing body 1130 extends into the outer housing body 1112 fromthe housing cover 1114. Referring to FIG. 30 , the inner housing body1130 has an open first end 1132 positioned inside the central opening1128 of the housing cover 1114 and an open second end 1134 opposite theopen first end 1132 positioned inside the outer housing body 1112. Anairtight seal may be formed between the open first end 1132 of the innerhousing body 1130 and the housing cover 1114 along the central opening1128. In the embodiment illustrated, the inner housing body 1130 has agenerally cylindrical outer shape with a generally circularcross-sectional shape. The open first end 1132 is in fluid communicationwith the interior through-channel 432 of the ventilation pipe 400.

The ventilator assembly 1100 has a fan assembly 1140 housed inside theouter housing 1110. The fan assembly 1140 may be configured to generatesufficient airflow to completely replace the internal atmosphere 104(see FIG. 3 ) with a portion of the external atmosphere 102 (see FIG. 3) within a predetermined amount of time (e.g., one day or one hour).Referring to FIG. 28 , the fan assembly 1140 includes a fan housing1142, a cover 1144, and one or more fan(s) 1150.

Referring to FIG. 30 , the fan housing 1142 is positioned inside theouter housing body 1112 with one or more vertical air channels 1154defined therebetween. Referring to FIG. 29 , in the embodimentillustrated, the fan housing 1142 has a generally triangularcross-sectional shape defined by substantially planar panels 1146, 1147,and 1148 (see FIG. 28 ) coupled together along their edges by brackets1156, 1157, and 1158. Referring to FIG. 30 , as mentioned above, theouter housing body 1112 may have a circular cross-sectional shape. Thus,in the embodiment illustrated, the fan housing 1142 has a differentcross-sectional shape than the outer housing body 1112. However, this isnot a requirement.

The fan housing 1142 has an open first end 1160 opposite an open secondend 1162. The open first end 1160 may be immediately adjacent thehousing cover 1114. The housing cover 1114 protects or shields thefan(s) 1150 from debris and water falling through the ventilation pipe400 from above the ventilator assembly 1100.

The inner housing body 1130 extends downwardly through the open firstend 1160 part way through the fan housing 1142. The cover 1144 iscoupled to and closes the open second end 1162 of the fan housing 1142.Thus, an internal chamber 1170 is defined within the fan housing 1142.The outer housing body 1112 extends beyond the inner housing body 1130to position the open second end 1122 of the outer housing body 1112 awayfrom the cover 1144.

Referring to FIG. 29 , in the embodiment illustrated, rods 1172-1174extend downwardly from the housing cover 1114 and through the internalchamber 1170. Distal ends 1176 of the rods 1172-1174 pass through thecover 1144. Fasteners F7 (e.g., wingnuts) are attached to (e.g.,threaded onto) the distal ends 1176 and removably couple the cover 1144in place.

One or more through-holes 1180 are formed in the fan housing 1142between its open first and second ends 1160 and 1162. In the embodimentillustrated, a different through-hole 1180 has been provided for eachfan 1150. Referring to FIG. 30 , each fan 1150 is mounted on the fanhousing 1142 and positioned to blow air into (or from) the internalchamber 1170 through the through-hole(s) 1180. In other words, referringto FIG. 30 , the fan(s) 1150 effect an air exchange between the airchannels 1154 and the internal chamber 1170. This air exchange causesair to flow into (or from) the open second end 1134 of the inner housingbody 1130, which causes air exchange between the inner housing body 1130and the interior through-channel 432 of the ventilation pipe 400 (viathe open first end 1132 of the inner housing body 1130).

When the fan assembly 1140 is blowing air into the vault 12 (see FIGS.1, 3-4B, 9A, 18, 19, 21A, 21B, 26A, and 32 ), that air travels from theexternal atmosphere 102 (see FIG. 3 ) through the manhole cover 230G(see FIGS. 21A-22B, 31, and 32 ) and into the ventilation pipe 400(e.g., the section P1). Next, the air enters the open first end 1132 ofthe inner housing body 1130, flows through the inner housing body 1130,and exits therefrom into the internal chamber 1170. The fan(s) 1150 blowair through the through-hole(s) 1180 from the internal chamber 1170,through the air channels 1154, and out the open second end 1122 of theouter housing body 1112. The air exiting the open second end 1122 (seeFIGS. 27 and 30 ) enters the ventilation pipe 400 (e.g., into the upperend 403 of the section P2). Referring to FIG. 21B, the ventilation pipe400 conducts the airflow to the second opening 448 and the airflowenters the vault 12 via the second opening 448.

On the other hand, referring to FIG. 21A, when the fan assembly 1140(see FIGS. 28 and 30 ) is blowing air (as exhaust) from the main chamber52 of the vault 12, a portion (“exhausted air”) of the internalatmosphere 104 (see FIG. 3 ) inside the main chamber 52 is pulled intothe second opening 448 of the ventilation pipe 400. Referring to FIG. 30, the exhausted air flows into the open second end 1122 of the outerhousing body 1112 from the ventilation pipe 400 (e.g., via the upper end403 of the section P2), travels through the air channels 1154, and isblown by the fan(s) 1150 through the through-holes 1180 into theinternal chamber 1170. Next, the exhausted air enters the open secondend 1134 of the inner housing body 1130, flows therethrough, and exitsits open first end 1132 into the ventilation pipe 400 (e.g., into thelower end 401 of the section P1). From that point, referring to FIG.21A, the exhausted air travels through the manhole cover 230G and intothe external atmosphere 102 (see FIG. 3 ).

Referring to FIG. 30 , the ventilator assembly 1100 illustrated may becharacterized as implementing a diving bell that helps protect thefan(s) 1150 when the vault 12 (see FIGS. 1, 3-4B, 9A, 18, 19, 21A, 21B,26A, and 32 ) is at least partially filled with water. Air inside theouter housing body 1112 may exit therefrom through either the innerhousing body 1130 or the open second end 1122 of the outer housing body1112. Thus, when both the open second end 1122 of the outer housing body1112 and the open second end 1134 of the inner housing body 1130 aresubmerged in water, any air trapped between the housing cover 1114, theinner housing body 1130, and the outer housing body 1112 cannot escapefrom inside the ventilator assembly 1100. Because the open second end1134 of the inner housing body 1130 is positioned below the fan(s) 1150,the fan(s) 1150 are positioned within the trapped air and protected frombeing fully submerged in the event of a flood. Thus, expensivesubmersible fans are not required to implement the ventilator assembly1100. Also, a complicated control system is not needed to shut-off thefan(s) 1150 during a flood event when the water reaches the ventilatorassembly 1100.

While the ventilator assembly 1100 has been illustrated as includingmultiple fans 1150, some implementation may include a single fan.Further, while each fan 1150 has been illustrated as being an axial fanthat uses blades (or propellers) to move air, alternate types of fans(e.g., centrifugal fans, radial fans, in-line radial fans, etc.) couldbe used. The fan(s) 1150 may be selected based on compatibility with theoperating environment (which may include water, salt, steam, freezingtemperatures, petrochemical exposure, life expectancy, spark-less motor,explosion proof, etc.) inside the vault 12 (see FIGS. 1, 3-4B, 9A, 18,19, 21A, 21B, 26A, and 32 ). The fan(s) 1150 may be IP55 rated, dustprotected, and/or water-jet protected. It may be desirable to implementthe fan(s) 1150 with fans configured to have a working lifespan of atleast a predetermined duration (e.g., about 50,000 hours) and/or tooperate within a predetermined temperature range (e.g., about −30° C. toabout 80° C.).

The fan(s) 1150 may be powered by alternating current (“AC”). By way ofnon-limiting examples, the fan(s) 1150 may be configured to operatewithin a voltage range of 100 VAC to 120 VAC, 200 VAC to 240 VAC, or 440VAC to 480 VAC. When the fan assembly 1140 includes multiple fans 1150,they may be implemented as redundant fans powered by alternating current(“AC”) in parallel. Alternatively, direct current (“DC”) or three-phaseAC power may be used to power the fan(s) 1150.

Referring to FIG. 31 , power may be supplied to the ventilator assembly1100 by a connection 1190 to a power source. The power source may be thecable 110 (see FIGS. 3, 21A, and 32 ), which may be configured todeliver 120 VAC, 240 VAC, or 480 VAC. In such implementations, theconnection 1190 may include a splice 1194 onto the cable 110 (see FIGS.3, 21A, and 32 ) or an inductive coil positioned alongside the cable110. Alternatively, referring to FIG. 21A, if the vault 12 includes thewall plug/receptacle 1192, the connection 1190 (see FIGS. 21B and 31 )may simply include a conventional power cord with a plug configured tomate with and receive power from the plug/receptacle 1192. By way ofanother non-limiting example, referring to FIG. 21B, the connection 1190may draw parasitic power if no service voltage is available in the vault12. Optionally, referring to FIG. 32 , an inductive charging plate 1193may be installed in the vault 12 (e.g., on the floor 58) and theconnection 1190 (see FIGS. 21B and 31 ) may include an antenna 1195configured to receive power from the inductive charging plate 1193. Theantenna 1195 may extend (e.g., along the ventilation pipe 400) from theventilator assembly 1100 toward the inductive charging plate 1193. Theouter housing body 1112 (see FIGS. 27, 30, and 31 ) may provideconnection points for the connection 1190 (see FIGS. 21B and 31 ).

In the embodiment illustrated in FIG. 31 , the fan(s) 1150 (see FIGS.28-30 and 33 ) are connected to and receive power via a wire or cord1196 that extends outwardly from the outer housing body 1112 andterminates at a plug or power receptacle 1197. Alternatively, the cord1196 may be housed inside the outer housing body 1112 and the powerreceptacle 1197 may be mounted on the outer housing body 1112. Theconnection 1190 has a plug 1198 configured to mate with and supply powerto the power receptacle 1197. The connection 1190 receives power fromthe splice 1194 connected to the cable 110 as shown in FIG. 21A.

Referring to FIG. 31 , the worker 61 (see FIGS. 1 and 3 ) may manuallyconnect the plug 1198 of the connection 1190 to the power receptacle1197. Optionally, one or both of the plug 1198 and the power receptacle1197 may be magnetic to help maintain the connection therebetween andfacilitate connecting the two components together.

FIG. 32 illustrates the ventilation system 910 installed in the vault12. As shown in this figure, the ventilation system 910 may be used topull air from neighboring vaults 14 and 16 (via the conduits 20A-20C)and/or push air into the neighboring vaults 14 and 16 (via the conduits20A-20C). Thus, the ventilation system 910 need not be installed inevery vault within a system (e.g., the system 10 illustrated in FIG. 1 )to reduce manhole events. One or more second openings 448 may bepositioned near the conduits 20A-20C. For example, the conduits 20A-20Cmay each have one or more openings 1199 into the vault 12 and one ormore second openings 448 may be positioned near the opening(s) 1199 ofone or more of the conduits 20A-20C.

Referring to FIG. 21A, while the ventilator 410 of the ventilationsystem 910 has been illustrated as being implemented by the ventilatorassembly 1100 (see FIGS. 27 and 30-32 ), the ventilator 410 mayalternatively be implemented by the in-line heater 500 (see FIGS. 8A,8B, 9A, and 13A-13C) or the in-line fan 550 (see FIGS. 14A-14C). By wayof additional non-limiting examples, the ventilator 410 may beimplemented as a forced convection device, a powered bellows, acompressor, a piston pump, a piston ventilator, an in-line pump, a fan,a blower, a cartridge heater, a coil heater, or a heat-generating deviceconfigured to provide passive heating, such as a transformer, generator,compressor, and the like. It is also contemplated that a redundantsystem employing more than one type of air moving device (e.g., both thein-line fan 550 and the in-line heater 500) may be advantageous inparticularly critical applications. Further, more than one air movingdevice of the same type may be used.

While the ventilator assembly 1100 (see FIGS. 27 and 30-32 ) has beenillustrated as being a component of the ventilation system 910, theventilator assembly 1100 may alternatively be used to implement theventilator 410 of the ventilation system 210 illustrated in FIG. 4A orthe ventilation system 710 illustrated in FIG. 18 .

Optional Debris Catcher

Referring to FIG. 33 , an optional debris catcher 1200 may be coupled tothe inner housing body 1130 and positioned to catch debris falling fromthe open second end 1134 of the inner housing body 1130. The debriscatcher 1200 is configured to catch and store dirt, garbage, and otherdebris that enters the ventilation system 910 (see FIGS. 21A, 21B, and32 ) from the surface 30 (see FIGS. 1, 3-6C, 9A, 9B, 18, 19, 21A, 26A,and 32 ). In the embodiment illustrated, the debris catcher 1200 isgenerally bucket shaped and has an open first end 1204 opposite isclosed second end 1206. The open first end 1204 is positioned to receivedebris falling from the open second end 1134 of the inner housing body1130. The debris catcher 1200 may include through-holes 1210 configuredto receive fasteners F8 (fasteners) that removably couple the debriscatcher 1200 to the inner housing body 1130. The worker 61 (see FIGS. 1and 3 ) may empty the debris catcher 1200 whenever the ventilatorassembly 1100 is removed from the vault 12 (see FIGS. 1, 3-4B, 9A, 18,19, 21A, 21B, 26A, and 32 ).

Experimental

In a first series of experiments, several vented manhole coverconfigurations were evaluated with respect to ability to clear acontaminated gaseous composition from a simulated manhole vault, asfollows.

Test Apparatus

A test apparatus simulating a typical manhole vault was first fabricatedand is shown in schematic fashion in FIG. 34 . This figure illustratesthe case wherein a heated exhaust pipe and a manifold were employed, asin Assembly 4, described below. A wind tunnel 118 comprising a firstduct 119 having a diameter of 20 inches and containing a plurality of 2inch-diameter cardboard tubes 123 disposed therein in a close-packedconfiguration with all axes in parallel, was connected to the entranceside of a 2 foot tall manhole test chamber 122. Air was forced throughthe first duct 119 by a variable speed fan 121, as indicated by thelarge left-pointing arrow. A similar second duct 120, which alsocontained the small tubes 123, was connected to the exit side of thetest chamber 122. In each case, tubes 123 assured an essentially laminarair flow within chamber 122. Test chamber 122 was mounted atop a plywoodmanhole vault 200 having the dimensions 4 feet wide, 4 feet long, and 8feet tall, wherein joints were covered with caulk and tape to preventgas from escaping in an uncontrolled manner.

Air flow from fan 121 provided a simulated wind, which passed over thesurface of a 32 inch diameter test manhole cover 201, wherein the latterrested on a ledge in an opening at the bottom of the test chamber 122.In some of the experiments, a first end 140′ of a 4″ Sch. 10 steelexhaust pipe 140 was sealably connected to a corresponding port in thetest manhole cover 201 (i.e., either directly, or with the aid of amanifold as illustrated). When used, the exhaust pipe 140 was wrappedwith electrical heating tape substantially along its entire length (withan overlayer of fiberglass insulation; not shown) to provide an in-lineheater 150. The second (intake) end 140″ of the pipe 140 was positionedapproximately 9 inches above the floor 208 of vault 200. A 4-inchdiameter gas inlet pipe 124 near the bottom of vault 200 was used tointroduce a heavier-than-air gaseous composition into the vault.Concentration of this simulated contaminant was quantitatively monitoredwith the aid of a helium-neon laser source 126, mounted at floor level,and a light meter 128, mounted near the ceiling of the vault 200 and inalignment with the laser source 126.

Procedure

In order to evaluate the ventilation efficiency of various manhole coverdesigns the above described manhole vault 200 was filled with aheavier-than-air gaseous composition and the time required to clearessentially all of this composition from the vault was determined underdifferent simulated wind conditions, the shortest clearing time beingmost preferred. In these tests, the gaseous composition consisted of acommercial “Halloween Fog,” made from a solution of a glycol and water,this being delivered via gas inlet pipe 124 by a commercial householdfog machine following the manufacturer's instructions. During a typicaltest, the voltage output signal of the light meter 128 was recordedcontinuously by a data acquisition unit, this value being inverselyproportional to the fog density or directly proportional to theatmospheric clarity. As the fog cleared, this signal gradually increaseduntil it stabilized for about 10 minutes at a maximum reading, thisbeing designated as a cleared vault condition, which was also verifiedvisually. Using the above described apparatus, four different manholecover assembly configurations were evaluated with respect to vaultclearing time, wherein each manhole cover was a wooden mock-up of theparticular design being tested:

Assembly 1 (control) was the conventional vented manhole cover 70employed by ConEd of NY (see Background of the Invention). As shown inFIG. 2, this cover 70 had twelve vent holes 72 circumferentiallydisposed every 30 degrees near the periphery thereof, and twelve suchholes 72 disposed closer to the center of the cover, also every 30degrees. Each hole 72 had a diameter of 1⅛ inch. This control did notinclude a manifold, the exhaust pipe 140, or heater 150.

Assembly 2 was the same as Assembly 1 but included the heated exhaustpipe (i.e., pipe 140 and heater 150) connected to a manifold attached tothe underside of the manhole cover 70, the manifold encompassing theinner holes 72 shown in FIG. 2 .

Assembly 3 was essentially the design depicted in FIGS. 10A-10F (i.e.,including the manhole cover 230F, the round vent hole caps 652F, and theexhaust passage cap 280), which also included the exhaust pipe 140 withheater 150.

Assembly 4 was essentially the design depicted in FIGS. 8A-8I (i.e.,including the manhole cover 230D, the vent hole caps 652D and theexhaust hole caps 653D), which also includes the heated exhaust pipe.

In experiments wherein the exhaust pipe 140 was fluidly connected to themanhole cover being tested, it was heated by passing 110V electriccurrent through a heating cable (heater 150) wrapped around the exhaustpipe 140 which was overlaid with fiberglass blanket insulation, asdescribed above. The temperature of the pipe was controlled at 30° C.above ambient temperature before each test was started.

The results of evaluations of the artificial fog clearing efficiency ofthe above assemblies at various wind speeds is shown in FIG. 35 ,wherein the following symbols are used: ×=Assembly 1; ♦=Assembly 2;▪=Assembly 3; and ●=Assembly 4. From this figure, it can be seen that,even though Assembly 1 (the control vented manhole cover without theheated pipe) can sometimes clear the vault in less time than the othersystems evaluated when wind velocity is increased, all the assemblieswhich also employed the heated pipe according to the present inventionprovided significantly shorter clearing times in still air (i.e., windspeed=0). It is particularly noted that Assembly 4 according to thefirst preferred embodiment of the manhole cover had a “still air”clearing time about half that of the control.

As a verification that the above mentioned laser source 126 and lightmeter 128 produced reliable measures of the concentration of aheavier-than-air gas, separate evaluations using argon as the test gaswere carried out wherein the concentration of oxygen was detected withelectronic oxygen sensors placed at various points in the vault. Inthese tests, exhaust pipe 140 was not heated and the openings of coverAssembly 2 were first covered with tape. Argon was fed into the vault200 through gas inlet pipe 124 until the oxygen concentration was belowtwo volume percent at a sensor mounted on a wall approximately 1 inchabove the floor. At time zero of the test, the test manhole cover wasunsealed (i.e., the tape was removed from all holes in the manholecover) and the ventilation system was engaged. The test was terminatedwhen the oxygen concentration reached 20.9%, consistent with theatmosphere outside the chamber. FIG. 36 compares clearing times forargon gas (▴) and the above-described fog (▪) using the cover ofAssembly 2. It can be seen that the trend of the two tests is similar,but the argon clearing time without external wind is somewhat greaterthan that of the fog test, again demonstrating the difficulty ofremoving heavier-than-air gases in a windless environment. Theseevaluations confirm that the artificial fog is a good surrogate forargon and other heavier-than-air gases.

In a second series of experiments, the above described plywood manholevault 200 was fitted with a wooden test manhole cover similar to thevented manhole cover 70 shown in FIG. 2 , but having a 4 inch diametercentral hole in addition to the twenty-four 1⅛ inch holes alreadypresent. The cover was cut into two semi-circular halves to allow a 2foot-long heated (and insulated) aluminum pipe section having a flangeat each end thereof, as shown in FIGS. 13A-13C (i.e., in-line heater500) to be clamped within the central hole when the two halves of thecover were pushed together. The in-line heater 500 was thus supportedfrom the cover by its top flange. Four-inch diameter PVC exhaust pipesections having various lengths were connected to the lower flange ofthe in-line heater 500, and centered in the vault 200 to provideassemblies in which the exhaust pipe inlet height above the floor 208 ofthe vault 200 was set at the values indicated in the left column ofTable 1, below. In this table, “zero” height above the floor indicatesthat the intake end 140″ rested on the floor 208 and an approximately1/16 inch gap for gas remained between this end and the floor due to therough cut of exhaust pipe 140. Provision was made for the introductionof argon gas into the vault via a tube which distributed the gas todiffusers placed on the floor of the vault at various locations. A fuelcell-based oxygen sensor (Class R-17S, Teledyne Analytical Instruments)was placed in a corner of the vault approximately one inch above floorlevel and a signal therefrom was directed to an oxygen meter (MiniOx® I,MSA Medical Products) which displayed the oxygen concentration directly.A webcam recorded the oxygen meter's reading every second, and saved theresulting video to a computer.

In a typical procedure, a particular length of exhaust pipe was attachedto the in-line heater and tested as follows. The vault was closed, thein-line heater 500 temperature was set and maintained at 60° C., and thewebcam was turned on. All these tests were carried out without the abovedescribed simulated wind (i.e., with still air above the test manholecover). Argon was fed into the vault until the oxygen sensor indicated1.5% oxygen, whereupon gas flow was stopped and a ventilation test begun(time=0). Ventilation of the vault 200 via the exhaust pipe/in-lineheater combination was continued until the oxygen concentrationindicated by the sensor reached at least 20.5%, after which the webcamvideo was screened manually, with data being transcribed every 15minutes. In addition to these ventilation tests using various lengths ofthe exhaust pipe, two control tests were also run wherein only thein-line heater was suspended from the manhole cover, but the latter wasnot heated. In the first control (CO), the central hole of the manholecover was blocked while the 24 smaller holes remained open. Thisconfiguration is similar to the above mentioned vented manhole coveremployed by ConEd. In the second control (CC), both the central hole aswell as all of the smaller holes were covered with a rubber mat.

The oxygen concentration was plotted as a function of time for each pipelength tested, as well as for the two controls. The end point of thetest was the time at which the oxygen concentration was above 20.5% andthe derivative of the concentration-time curve was essentially zero. Theventilation results so obtained were then ranked based on the calculatedarea under the concentration-time curve for each condition tested,wherein the open control (CO) result served as a basis for comparison.Thus, the ratio of the area under the (CO) control curve to the areaunder the curve for a given exhaust pipe length was calculated anddesignated the “Clearing Ratio.” This ratio is reported in the rightcolumn of Table 1, wherein higher values indicate more effective removalof the heavier-than-air argon from the lower regions of the vault. Itshould be apparent that the clearing ratio for the open control (CO) is1.00 by definition.

From Table 1 it is seen that the preferred pipe inlet height forclearing the argon most efficiently was 6 inches off the floor and thepreferred range is 0 to 36 inches off the floor, wherein the clearingratio is greater than 1 (i.e., the open control). Surprisingly, ventsystems wherein the exhaust pipe inlet was 48 to 72 inches above floorlevel were even less effective than the open control, indicating thatsome venting systems can actually hinder ventilation of heavier-than-airgases.

TABLE 1 Height of Exhaust Pipe Clearing Inlet Above Floor (inches) Ratio “0” 2.00  3 2.01  6 3.16  9 2.42 12 2.11 24 2.13 36 1.32 48 0.58 600.65 72 0.68 Closed Control 0.74 Open Control 1.00

The foregoing described embodiments depict different componentscontained within, or connected with, different other components. It isto be understood that such depicted architectures are merely exemplary,and that in fact many other architectures can be implemented whichachieve the same functionality. In a conceptual sense, any arrangementof components to achieve the same functionality is effectively“associated” such that the desired functionality is achieved. Hence, anytwo components herein combined to achieve a particular functionality canbe seen as “associated with” each other such that the desiredfunctionality is achieved, irrespective of architectures or intermedialcomponents. Likewise, any two components so associated can also beviewed as being “operably connected,” or “operably coupled,” to eachother to achieve the desired functionality.

While particular embodiments of the present invention have been shownand described, it will be obvious to those skilled in the art that,based upon the teachings herein, changes and modifications may be madewithout departing from this invention and its broader aspects and,therefore, the appended claims are to encompass within their scope allsuch changes and modifications as are within the true spirit and scopeof this invention. Furthermore, it is to be understood that theinvention is solely defined by the appended claims. It will beunderstood by those within the art that, in general, terms used herein,and especially in the appended claims (e.g., bodies of the appendedclaims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.). It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to inventions containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should typically be interpreted to mean “atleast one” or “one or more”); the same holds true for the use ofdefinite articles used to introduce claim recitations. In addition, evenif a specific number of an introduced claim recitation is explicitlyrecited, those skilled in the art will recognize that such recitationshould typically be interpreted to mean at least the recited number(e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations).

Accordingly, the invention is not limited except as by the appendedclaims.

The invention claimed is:
 1. A manhole cover for use with a ventilationpipe and for positioning in a manhole opening providing access to aninterior of a manhole vault, an external atmosphere being outside themanhole vault, the interior containing an internal atmosphere, themanhole cover comprising: a top surface positioned in the externalatmosphere when the manhole cover is positioned in the manhole opening;a bottom surface positioned in the internal atmosphere when the manholecover is positioned in the manhole opening; a plurality of through-holesextending between the top and bottom surfaces, the top surfacecomprising a plurality of channels that define a plurality of dam-likeportions, a different one of the plurality of dam-like portionssurrounding each of the plurality of through-holes, the plurality ofdam-like portions being configured to help prevent surface water fromentering the plurality of through-holes; a circular peripheral edge, acircular one of the plurality of channels separating a first portion ofthe plurality of through-holes from a second portion of the plurality ofthrough-holes, the first portion being positioned inside a boundarydefined by the circular channel, the second portion being positionedbetween the circular channel and the circular peripheral edge; aring-shaped wall attached to the bottom surface that surrounds the firstportion of the plurality of through-holes, the ring-shaped wall beingconnectable to the ventilation pipe and, when attached to theventilation pipe, helping to isolate a first airflow flowing inside theventilation pipe and through the first portion of the plurality ofthrough-holes from a second airflow flowing outside the ventilation pipeand through the second portion of the plurality of through-holes; acenter portion; a structure attached to the center portion on the bottomsurface; and a plurality of support walls attached to the bottom surfaceand extending radially from the structure through the ring-shaped walland toward the circular peripheral edge, each of the plurality ofsupport walls having a tapered distal end portion that terminates beforereaching the circular peripheral edge.
 2. The manhole cover of claim 1,further comprising: a center portion surrounded by the first portion ofthe plurality of through-holes.
 3. The manhole cover of claim 2, whereinthe first portion are outlet through-holes and the second portion areinlet through-holes.
 4. The manhole cover of claim 1, furthercomprising: a plurality of wells that extend inwardly from the circularperipheral edge, the wells being usable to lift the manhole cover fromthe manhole opening.
 5. The manhole cover of claim 1, wherein at least aportion of the first portion of the plurality of through-holes havedifferent sizes.
 6. The manhole cover of claim 1, wherein the secondportion of the plurality of through-holes are elongated and extendradially.
 7. The manhole cover of claim 1, further comprising: a centerportion positioned within the boundary, the plurality of through-holesbeing spaced apart from the center portion.
 8. The manhole cover ofclaim 7, wherein a dividing one of the plurality of channels separatesthe first portion from the center portion.
 9. The manhole cover of claim7, wherein the top surface has a dome shape that curves downwardly fromthe center portion toward the circular peripheral edge.
 10. The manholecover of claim 1, wherein the first portion is positioned between thestructure and the ring-shaped wall, and the second portion is positionedbetween the ring-shaped wall and the circular peripheral edge.
 11. Themanhole cover of claim 1 for use with a support bracket assemblycomprising a first ring-shaped wall that is connectable to theventilation pipe, wherein the ring-shaped wall of the manhole cover is asecond ring-shaped wall, the second ring-shaped wall of the manholecover is couplable to the first ring-shaped wall of the support bracketassembly with an upper edge portion of the first ring-shaped wall beingin contact with or adjacent to the second ring-shaped wall of themanhole cover.
 12. The manhole cover of claim 11, further comprising: aseal positionable between the first and second ring-shaped walls.